Management

Investment manager: Legg Mason Partners Fund Advisor, LLC

Subadviser: QS Investors, LLC (“QS Investors”)

Portfolio managers: Adam J. Petryk, CFA, Thomas Picciochi, CAIA, and Ellen Tesler. Mr. Petryk (Head of Multi-Asset and Solutions of QS Investors) has been a portfolio manager for the fund since June 2016. Mr. Picciochi (Head of Multi-Asset Portfolio Management Implementation of QS Investors) and Ms. Tesler (Portfolio Manager of QS Investors) have been portfolio managers for the fund since May 2014.

Purchase and sale of fund shares

You may purchase, redeem or exchange shares of the fund each day the New York Stock Exchange is open, at the fund’s net asset value determined after receipt of your request in good order, subject to any applicable sales charge.

The fund’s initial and subsequent investment minimums generally are set forth in the accompanying table:

Your Service Agent may impose different investment minimums.

For more information about how to purchase, redeem or exchange shares, and to learn which classes of shares are available to you, you should contact your Service Agent, or, if you hold your shares or plan to purchase shares through the fund, you should contact the fund by phone at 1-877-721-1926, by regular mail at Legg Mason Funds, P.O. Box 9699, Providence, RI 02940-9699 or by express, certified or registered mail at Legg Mason Funds, 4400 Computer Drive, Westborough, MA 01581.

Tax information

The fund’s distributions are generally taxable as ordinary income or capital gain.

Payments to broker/dealers and other financial intermediaries

The fund’s related companies may pay Service Agents for the sale of fund shares, shareholder services and other purposes. These payments create a conflict of interest by influencing your Service Agent or its employees or associated persons to recommend the fund over another investment. Ask your financial adviser or salesperson or visit your Service Agent’s or salesperson’s website for more information.

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QS Moderate Growth Fund

Investment objective

The fund seeks long-term growth of capital.

Fees and expenses of the fund

The accompanying table describes the fees and expenses that you may pay if you buy and hold shares of the fund.

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in funds distributed through Legg Mason Investor Services, LLC (“LMIS”), the fund’s distributor. More information about these and other discounts is available from your Service Agent, in this Prospectus on page 56 under the heading “Sales charges,” in the appendix titled “Appendix: Waivers and Discounts Available from Certain Service Agents” on page 91 of this Prospectus and in the fund’s statement of additional information (“SAI”) on page 74 under the heading “Sales Charge Waivers and Reductions for Class A Shares.” “Service Agents” include banks, brokers, dealers, insurance companies, investment advisers, financial consultants or advisers, mutual fund supermarkets and other financial intermediaries that have entered into an agreement with LMIS to sell shares of the fund.

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Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes:

Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover. The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 21% of the average value of its portfolio.

Principal investment strategies

The fund is a fund of funds—it invests in other mutual funds and exchange-traded funds (ETFs”). The fund is managed as an asset allocation program and allocates its assets among funds and ETFs managed by the manager and its affiliates and ETFs managed by unaffiliated investment advisers (underlying funds). The fund’s ability to invest in ETFs—whether managed by the manager or its affiliates or by unaffiliated investment advisers—will be effective as of July 1, 2017. After July 1, 2017, the portfolio managers will be able to allocate investments among underlying funds that are mutual funds and ETFs.

The fund organizes its investments in underlying funds into two main asset classes: the equity class (equity securities of all types) and the fixed income class (fixed income securities of all types). The portfolio managers may invest across all asset classes and strategies. The portfolio managers will allocate between 55% to 85% of the fund’s assets to underlying funds that invest in equity and equity-like strategies and between 15% to 45% of the fund’s assets to underlying funds that invest in fixed income strategies. The portfolio managers may, however, allocate fund assets to any underlying funds in varying amounts in a manner consistent with the fund’s investment objective. The fund’s allocation to each class will be measured at the time of purchase and may vary thereafter as a result of market movements.

The portfolio managers will seek to maintain a level of risk in the fund similar to that of the fund’s composite benchmark as defined under “Performance” below.

The underlying funds have a range of investment styles and focuses. The underlying funds may invest in foreign and emerging markets and engage in derivative transactions. The underlying equity funds may include exposure to any market cap or investment style including alternative investments (such as commodities, real estate assets and infrastructure assets). The underlying equity funds may employ strategies similar to those used by hedge funds, which may have a low correlation to broad stock market movements or take both long and short positions in equity securities. The underlying fixed income funds include funds investing in any sector, region or style, including foreign fixed income strategies, currency strategies,

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Principal investment strategies cont’d

inflation-indexed securities, structured credit and distressed debt. The underlying funds may take both long and short positions in fixed income securities. Such funds may also seek to profit from changes in global financial markets and take positions to take advantage of changes in interest rates, exchange rates, liquidity and other macroeconomic factors. The fixed income funds may also invest in securities having maturities of any length and any credit quality, including securities rated below investment grade (commonly known as “junk” bonds). The portfolio managers may invest the fund’s assets in underlying funds that have a limited performance history.

Principal risks

Risk is inherent in all investing. The value of your investment in the fund, as well as the amount of return you receive on your investment, may fluctuate significantly. You may lose part or all of your investment in the fund or your investment may not perform as well as other similar investments. The following is a summary description of certain risks of investing in the fund.

Affiliated funds risk. The fund’s manager serves as manager of the underlying Legg Mason funds and ETFs and Western Asset funds and is affiliated with the manager of the underlying Royce funds. In addition, the fund may invest in certain underlying funds (including ETFs) for which the fund’s subadviser serves as adviser. It is possible that a conflict of interest among the fund and the underlying funds could affect how the fund’s manager and subadviser fulfill their fiduciary duties to the fund and the underlying funds. For example, the subadviser may have an incentive to allocate the fund’s assets to those funds for which the fees paid to the manager or subadviser are higher than the fees paid by other underlying funds or to those funds for which the subadviser serves as adviser. However, the fund’s Board of Trustees believes the fund has been structured to mitigate these concerns.

Asset class variation risk. The underlying funds invest principally in the securities constituting their asset class ( i.e. , equity or fixed income). However, under normal market conditions, an underlying fund may vary the percentage of its assets in these securities (subject to any applicable regulatory requirements).

Credit risk. If an issuer or guarantor of a security held by an underlying fund or a counterparty to a financial contract with an underlying fund defaults or is downgraded, or is perceived to be less creditworthy, or if the value of the assets underlying a security declines, the value of your investment will typically decline. Subordinated securities are more likely to suffer a credit loss than non-subordinated securities of the same issuer and will be disproportionately affected by a default, downgrade or perceived decline in creditworthiness.

Currency risk. The value of investments in securities denominated in foreign currencies increases or decreases as the rates of exchange between those currencies and the U.S. dollar change. Currency conversion costs and currency fluctuations could erase investment gains or add to investment losses. Currency exchange rates can be volatile, and are affected by factors such as general economic conditions, the actions of the U.S. and foreign governments or central banks, the imposition of currency controls and speculation.

Cybersecurity risk. Cybersecurity incidents may allow an unauthorized party to gain access to fund assets, customer data (including private shareholder information), or proprietary information, or cause the fund, the manager, the subadvisers and/or their service providers (including, but not limited to, fund accountants, custodians, sub-custodians, transfer agents and financial intermediaries) to suffer data breaches, data corruption or lose operational functionality.

Derivatives risk. Using derivatives can increase an underlying fund’s losses and reduce opportunities for gains when market prices, interest rates, currencies or the derivatives themselves, behave in a way not anticipated by the underlying fund. Using derivatives also can have a leveraging effect and increase fund volatility. Certain derivatives have the potential for unlimited loss, regardless of the size of the initial investment. Derivatives may be difficult to sell, unwind or value, and the counterparty may default on its obligations to the underlying fund. Derivatives are generally subject to the risks applicable to the assets, rates, indices or other indicators underlying the derivative. The value of a derivative may fluctuate more than the underlying assets, rates, indices or other indicators to which it relates. Use of derivatives may have different tax consequences for an underlying fund than an investment in the underlying security, and those differences may affect the amount, timing and character of income distributed to shareholders. The U.S. government and foreign governments are in the process of adopting and implementing regulations governing derivatives markets, including mandatory clearing of certain derivatives, margin and reporting requirements. The ultimate impact of the regulations remains unclear. Additional regulation of derivatives may make derivatives more costly, limit their availability or utility, otherwise adversely affect their performance or disrupt markets. In addition, the SEC has proposed a new rule that would change the regulation of the use of derivatives by registered investment companies, such as an underlying fund. If the proposed rule takes effect, it could limit the ability of an underlying fund to invest in derivatives.

Credit default swap contracts involve heightened risks and may result in losses to an underlying fund. Credit default swaps may be illiquid and difficult to value, and they increase credit risk since the underlying fund has exposure to both the issuer whose credit is the subject of the swap and the counterparty to the swap.

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ETFs risk. Investing in an ETF will give the fund exposure to the securities comprising the index on which the ETF is based and will expose the fund to risks similar to those of investing directly in those securities. Shares of ETFs are traded on an exchange and may trade at either a premium or a discount to net asset value. The fund will pay brokerage commissions in connection with the purchase and sale of shares of ETFs.

Extension risk. If interest rates rise, repayments of fixed income securities may occur more slowly than anticipated by the market. This may drive the prices of these securities down because their interest rates are lower than the current interest rate and they remain outstanding longer.

Fixed income securities risk. Fixed income securities are subject to a number of risks, including credit, market and interest rate risks. Credit risk is the risk that the issuer or obligor will not make timely payments of principal and interest. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of an underlying fund’s investment in that issuer. The fund or underlying fund is subject to greater levels of credit risk to the extent an underlying fund holds below investment grade debt securities, or “junk” bonds. Market risk is the risk that the fixed income markets may become volatile and less liquid, and the market value of an investment may move up or down, sometimes quickly or unpredictably. Interest rate risk is the risk that the value of a fixed income security will fall when interest rates rise.

Foreign investments and emerging market risk. An underlying fund’s investments in securities of foreign issuers or issuers with significant exposure to foreign markets involve additional risk. Foreign countries in which an underlying fund may invest may have markets that are less liquid, less regulated and more volatile than U.S. markets. The value of an underlying fund’s investments may decline because of factors affecting the particular issuer as well as foreign markets and issuers generally, such as unfavorable or unsuccessful government actions, reduction of government or central bank support and political or financial instability. Lack of information may also affect the value of these securities. To the extent an underlying fund focuses its investments in a single country or only a few countries in a particular geographic region, economic, political, regulatory or other conditions affecting such country or region may have a greater impact on fund performance relative to a more geographically diversified fund.

The risks of foreign investments are heightened when investing in issuers in emerging market countries. Emerging market countries tend to have economic, political and legal systems that are less fully developed and are less stable than those of more developed countries. They are often particularly sensitive to market movements because their market prices tend to reflect speculative expectations. Low trading volumes may result in a lack of liquidity and in extreme price volatility.

Growth and value investing risk. Growth or value securities as a group may be out of favor and underperform the overall equity market while the market concentrates on other types of securities. Growth securities typically are very sensitive to market movements because their market prices tend to reflect future expectations. When it appears those expectations will not be met, the prices of growth securities typically fall. Growth securities may also be more volatile than other investments because they often do not pay dividends. The value approach to investing involves the risk that stocks may remain undervalued. An underlying fund that is growth- or value-oriented may, like many growth or value funds, weight its investments toward certain industries, thus increasing its exposure to factors adversely affecting issuers within those industries and, indirectly, the fund’s exposure to those factors.

Hedge fund strategies risk. The fund, through the underlying funds, may employ investment strategies that involve greater risks than the strategies used by typical mutual funds, including increased use of short sales, leverage and derivative transactions and hedging strategies. The fund may invest in underlying funds employing proprietary investment strategies that are not fully disclosed, which may involve risks that are not anticipated.

High yield (“junk”) bonds risk. High yield bonds are generally subject to greater credit risks than higher-grade bonds, including the risk of default on the payment of interest or principal. High yield bonds are considered speculative, tend to be less liquid and are more difficult to value than higher grade securities. High yield bonds tend to be volatile and more susceptible to adverse events, credit downgrades and negative sentiments and may be difficult to sell at a desired price, or at all, during periods of uncertainty or market turmoil.

Investing in a fund of funds risk. Your cost of investing in the fund, as a fund of funds, may be higher than the cost of investing in a mutual fund that only invests directly in individual equity and fixed income securities. An underlying fund may change its investment objective or policies without the fund’s approval, which could force the fund to withdraw its investment from such underlying fund at a time that is unfavorable to the fund. In addition, one underlying fund may buy the same securities that another underlying fund sells. Therefore, the fund would indirectly bear the costs of these trades without accomplishing any investment purpose. If the fund invests in an underlying fund that has recently commenced operations, there can be no assurance that such underlying fund will grow to or maintain an economically viable size, in which case the underlying fund’s board or adviser may determine to liquidate the underlying fund.

Issuer risk. The value of a security can go up or down more than the market as a whole and can perform differently from the value of the market as a whole, often due to disappointing earnings reports by the issuer, unsuccessful products or services, loss of major customers, major litigation against the issuer or changes in government regulations affecting the issuer or the competitive environment. An underlying fund may experience a substantial or complete loss on an individual security.

Large capitalization company risk. Large capitalization companies may fall out of favor with investors based on market and economic conditions. In return for the relative stability and low volatility of large capitalization companies, an underlying fund’s value may not rise as much as the value of funds that invest in companies with smaller market capitalizations.

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Principal risks cont’d

Liquidity risk. Some assets held by an underlying fund may be impossible or difficult to sell, particularly during times of market turmoil. These illiquid assets may also be difficult to value. Markets may become illiquid when, for instance, there are few, if any, interested buyers or sellers or when dealers are unwilling or unable to make a market for certain securities. As a general matter, dealers recently have been less willing to make markets for fixed income securities. If an underlying fund is forced to sell an illiquid asset to meet redemption requests or other cash needs, the underlying fund may be forced to sell at a loss.

Long/short strategy risk. While an underlying fund may invest in long positions and short positions, there is the risk that the investments will not perform as expected and losses on one type of position could more than offset gains on the other, or the underlying fund could lose money on both positions, if the adviser judges the market incorrectly.

Market events risk. In the past several years financial markets, such as those in the United States, Europe, Asia and elsewhere, have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty. Governmental and non-governmental issuers have defaulted on, or been forced to restructure, their debts. These conditions may continue, recur, worsen or spread. Events that have contributed to these market conditions include, but are not limited to major cybersecurity events; measures to address U.S. federal and state budget deficits; downgrading of U.S. long-term sovereign debt; declines in oil and commodity prices; dramatic changes in currency exchange rates; and public sentiment.

The U.S. government and the Federal Reserve, as well as certain foreign governments and central banks, have taken steps to support financial markets, including by keeping interest rates at historically low levels. This and other government intervention may not work as intended, particularly if the efforts are perceived by investors as being unlikely to achieve the desired results. The Federal Reserve has reduced its market support activities and recently has begun raising interest rates. Certain foreign governments and central banks are implementing or discussing so-called negative interest rates (e.g., charging depositors who keep their cash at a bank) to spur economic growth. Further Federal Reserve or other U.S. or non-U.S. governmental or central bank actions, including interest rate increases or contrary actions by different governments, could negatively affect financial markets generally, increase market volatility and reduce the value and liquidity of securities in which the fund or an underlying fund invests.

Policy and legislative changes in the United States and in other countries are affecting many aspects of financial regulation, and may in some instances contribute to decreased liquidity and increased volatility in the financial markets. The impact of these changes on the markets, and the practical implications for market participants, may not be fully known for some time.

Economies and financial markets throughout the world are increasingly interconnected. Economic, financial or political events, trading and tariff arrangements, terrorism, natural disasters and other circumstances in one country or region could have profound impacts on global economies or markets. As a result, whether or not the fund or an underlying fund invests in securities of issuers located in or with significant exposure to the countries directly affected, the value and liquidity of the fund’s or underlying fund’s investments may be negatively affected.

Non-diversification risk. The fund is classified as “non-diversified,” which means it may invest a larger percentage of its assets in a smaller number of underlying funds than a diversified fund. To the extent the fund invests its assets in a smaller number of underlying funds, the fund will be more susceptible to negative events affecting those funds than diversified funds. The underlying funds in which the fund invests may be either diversified or non-diversified.

Prepayment or call risk. Many issuers have a right to prepay their securities. If interest rates fall, an issuer may exercise this right. If this happens, an underlying fund will not benefit from the rise in market price that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds at a time when yields on securities available in the market are lower than the yield on the prepaid security. An underlying fund also may lose any premium it paid on the security.

Real assets risk. Investments by the fund in an underlying fund that invests in real assets involve a high degree of risk, including significant financial, operating, and competitive risks. Real assets include properties, natural resources, commodities and infrastructure assets. Investments in underlying funds that invest in real assets expose the fund to adverse macroeconomic conditions, such as a rise in interest rates or a downturn in the economy in which the asset is located, elevating the risk of loss.

Selection risk. The fund’s ability to achieve its investment goal depends upon the portfolio managers’ skill in determining the fund’s strategic asset class allocation and in selecting the best mix of underlying funds. The value of your investment may decrease if the portfolio managers’ judgment about the attractiveness, value or market trends affecting a particular asset class, investment style, underlying fund or other issuer is incorrect.

Small and medium capitalization company risk. An underlying fund will be exposed to additional risks as a result of its investments in the securities of small and medium capitalization companies. Small and medium capitalization companies may fall out of favor with investors; may have limited product lines, operating histories, markets or financial resources; or may be dependent upon a limited management group. The prices of securities of small and medium capitalization companies generally are more volatile than those of large capitalization companies and are more likely to be adversely affected than large capitalization companies by changes in earnings results and investor expectations or poor economic or market conditions, including those experienced during a recession. Securities of small and medium capitalization companies may underperform large

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capitalization companies, may be harder to sell at times and at prices the portfolio managers believe appropriate and may offer greater potential for losses.

Stock market and equity securities risk. The securities markets are volatile and the market prices of the fund’s or an underlying fund’s securities may decline generally. Securities fluctuate in price based on changes in a company’s financial condition and overall market and economic conditions. If the market prices of the securities owned by the fund or an underlying fund fall, the value of your investment in the fund will decline.

Valuation risk. The sales price an underlying fund could receive for any particular portfolio investment may differ from the underlying fund’s valuation of the investment, particularly for securities that trade in thin or volatile markets or that are valued using a fair value methodology. Investors who purchase or redeem fund shares on days when an underlying fund is holding fair-valued securities may receive fewer or more shares or lower or higher redemption proceeds than they would have received if the underlying fund had not fair-valued securities or had used a different valuation methodology. The fund’s and underlying fund’s ability to value their investments may be impacted by technological issues and/or errors by pricing services or other third party service providers.

These risks are discussed in more detail later in this Prospectus or in the SAI.

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Management

Investment manager: Legg Mason Partners Fund Advisor, LLC

Subadviser: QS Investors, LLC (“QS Investors”)

Portfolio managers: Adam J. Petryk, CFA, Thomas Picciochi, CAIA, and Ellen Tesler. Mr. Petryk (Head of Multi-Asset and Solutions of QS Investors) has been a portfolio manager for the fund since June 2016. Mr. Picciochi (Head of Multi-Asset Portfolio Management Implementation of QS Investors) and Ms. Tesler (Portfolio Manager of QS Investors) have been portfolio managers for the fund since May 2014.

Purchase and sale of fund shares

You may purchase, redeem or exchange shares of the fund each day the New York Stock Exchange is open, at the fund’s net asset value determined after receipt of your request in good order, subject to any applicable sales charge.

The fund’s initial and subsequent investment minimums generally are set forth in the accompanying table:

Your financial intermediary may impose different investment minimums.

For more information about how to purchase, redeem or exchange shares, and to learn which classes of shares are available to you, you should contact your financial intermediary, or, if you hold your shares or plan to purchase shares through the fund, you should contact the fund by phone at 1-877-721-1926, by regular mail at Legg Mason Funds, P.O. Box 9699, Providence, RI 02940-9699 or by express, certified or registered mail at Legg Mason Funds, 4400 Computer Drive, Westborough, MA 01581.

Tax information

The fund’s distributions are generally taxable as ordinary income or capital gain.

Payments to broker/dealers and other financial intermediaries

The fund’s related companies may pay Service Agents for the sale of fund shares, shareholder services and other purposes. These payments create a conflict of interest by influencing your Service Agent or its employees or associated persons to recommend the fund over another investment. Ask your financial adviser or salesperson or visit your financial intermediary’s or salesperson’s website for more information.

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QS Conservative Growth Fund

Investment objective

The fund seeks balance of growth of capital and income.

Fees and expenses of the fund

The accompanying table describes the fees and expenses that you may pay if you buy and hold shares of the fund.

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in funds distributed through Legg Mason Investor Services, LLC (“LMIS”), the fund’s distributor. More information about these and other discounts is available from your Service Agent, in this Prospectus on page 56 under the heading “Sales charges,” in the appendix titled “Appendix: Waivers and Discounts Available from Certain Service Agents” on page 91 of this Prospectus and in the fund’s statement of additional information (“SAI”) on page 74 under the heading “Sales Charge Waivers and Reductions for Class A Shares.” Service Agents” include banks, brokers, dealers, insurance companies, investment advisers, financial consultants or advisers, mutual fund supermarkets and other financial intermediaries that have entered into an agreement with LMIS to sell shares of the fund.

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Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes:

Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover. The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 20% of the average value of its portfolio.

Principal investment strategies

The fund is a fund of funds—it invests in other mutual funds and ETFs. The fund is managed as an asset allocation program and allocates its assets among funds and ETFs managed by the manager and its affiliates and ETFs managed by unaffiliated investment advisers (underlying funds). The fund’s ability to invest in ETFs—whether managed by the manager or its affiliates or by unaffiliated investment advisers—will be effective as of July 1, 2017. After July 1, 2017, the portfolio managers will be able to allocate investments among underlying funds that are mutual funds and ETFs.

The fund organizes its investments in underlying funds into two main asset classes: the equity class (equity securities of all types) and the fixed income class (fixed income securities of all types). The portfolio managers may invest across all asset classes and strategies. The portfolio managers will allocate between 35% to 65% of the fund’s assets to underlying funds that invest in equity and equity-like strategies and between 35% to 65% of the fund’s assets to underlying funds that invest in fixed income strategies. The portfolio managers may, however, allocate fund assets to any underlying funds in varying amounts in a manner consistent with the fund’s investment objective. The fund’s allocation to each class will be measured at the time of purchase and may vary thereafter as a result of market movements.

The portfolio managers will seek to maintain a level of risk in the fund similar to that of the fund’s composite benchmark as defined under “Performance” below.

The underlying funds have a range of investment styles and focuses. The underlying funds may invest in foreign and emerging markets and engage in derivative transactions. The underlying equity funds may include exposure to any market cap or investment style including alternative investments (such as commodities, real estate assets and infrastructure assets). The underlying equity funds may employ strategies similar to those used by hedge funds, which may have a low correlation to broad stock market movements or take both long and short positions in equity securities. The underlying fixed income funds include funds investing in any sector, region or style, including foreign fixed income strategies, currency strategies, inflation-indexed securities, structured credit and distressed debt. The underlying funds may take both long and short positions in fixed income

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Principal investment strategies cont’d

securities. Such funds may also seek to profit from changes in global financial markets and take positions to take advantage of changes in interest rates, exchange rates, liquidity and other macroeconomic factors. The fixed income funds may also invest in securities having maturities of any length and any credit quality, including securities rated below investment grade (commonly known as “junk” bonds). The portfolio managers may invest the fund’s assets in underlying funds that have a limited performance history.

Principal risks

Risk is inherent in all investing. The value of your investment in the fund, as well as the amount of return you receive on your investment, may fluctuate significantly. You may lose part or all of your investment in the fund or your investment may not perform as well as other similar investments. The following is a summary description of certain risks of investing in the fund.

Affiliated funds risk. The fund’s manager serves as manager of the underlying Legg Mason funds and ETFs and Western Asset funds and is affiliated with the manager of the underlying Royce funds. In addition, the fund may invest in certain underlying funds (including ETFs) for which the fund’s subadviser serves as adviser. It is possible that a conflict of interest among the fund and the underlying funds could affect how the fund’s manager and subadviser fulfill their fiduciary duties to the fund and the underlying funds. For example, the subadviser may have an incentive to allocate the fund’s assets to those funds for which the fees paid to the manager or subadviser are higher than the fees paid by other underlying funds or to those funds for which the subadviser serves as adviser. However, the fund’s Board of Trustees believes the fund has been structured to mitigate these concerns.

Asset class variation risk. The underlying funds invest principally in the securities constituting their asset class ( i.e. , equity or fixed income). However, under normal market conditions, an underlying fund may vary the percentage of its assets in these securities (subject to any applicable regulatory requirements).

Credit risk. If an issuer or guarantor of a security held by an underlying fund or a counterparty to a financial contract with an underlying fund defaults or is downgraded, or is perceived to be less creditworthy, or if the value of the assets underlying a security declines, the value of your investment will typically decline. Subordinated securities are more likely to suffer a credit loss than non-subordinated securities of the same issuer and will be disproportionately affected by a default, downgrade or perceived decline in creditworthiness.

Currency risk. The value of investments in securities denominated in foreign currencies increases or decreases as the rates of exchange between those currencies and the U.S. dollar change. Currency conversion costs and currency fluctuations could erase investment gains or add to investment losses. Currency exchange rates can be volatile, and are affected by factors such as general economic conditions, the actions of the U.S. and foreign governments or central banks, the imposition of currency controls and speculation.

Cybersecurity risk. Cybersecurity incidents may allow an unauthorized party to gain access to fund assets, customer data (including private shareholder information), or proprietary information, or cause the fund, the manager, the subadvisers and/or their service providers (including, but not limited to, fund accountants, custodians, sub-custodians, transfer agents and financial intermediaries) to suffer data breaches, data corruption or lose operational functionality.

Derivatives risk. Using derivatives can increase an underlying fund’s losses and reduce opportunities for gains when market prices, interest rates, currencies or the derivatives themselves, behave in a way not anticipated by the underlying fund. Using derivatives also can have a leveraging effect and increase fund volatility. Certain derivatives have the potential for unlimited loss, regardless of the size of the initial investment. Derivatives may be difficult to sell, unwind or value, and the counterparty may default on its obligations to the underlying fund. Derivatives are generally subject to the risks applicable to the assets, rates, indices or other indicators underlying the derivative. The value of a derivative may fluctuate more than the underlying assets, rates, indices or other indicators to which it relates. Use of derivatives may have different tax consequences for an underlying fund than an investment in the underlying security, and those differences may affect the amount, timing and character of income distributed to shareholders. The U.S. government and foreign governments are in the process of adopting and implementing regulations governing derivatives markets, including mandatory clearing of certain derivatives, margin and reporting requirements. The ultimate impact of the regulations remains unclear. Additional regulation of derivatives may make derivatives more costly, limit their availability or utility, otherwise adversely affect their performance or disrupt markets. In addition, the SEC has proposed a new rule that would change the regulation of the use of derivatives by registered investment companies, such as an underlying fund. If the proposed rule takes effect, it could limit the ability of an underlying fund to invest in derivatives.

Credit default swap contracts involve heightened risks and may result in losses to an underlying fund. Credit default swaps may be illiquid and difficult to value, and they increase credit risk since the underlying fund has exposure to both the issuer whose credit is the subject of the swap and the counterparty to the swap.

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ETFs risk. Investing in an ETF will give the fund exposure to the securities comprising the index on which the ETF is based and will expose the fund to risks similar to those of investing directly in those securities. Shares of ETFs are traded on an exchange and may trade at either a premium or discount to net asset value. The fund will pay brokerage commissions in connection with the purchase and sale of shares of ETFs.

Extension risk. If interest rates rise, repayments of fixed income securities may occur more slowly than anticipated by the market. This may drive the prices of these securities down because their interest rates are lower than the current interest rate and they remain outstanding longer.

Fixed income securities risk. Fixed income securities are subject to a number of risks, including credit, market and interest rate risks. Credit risk is the risk that the issuer or obligor will not make timely payments of principal and interest. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of an underlying fund’s investment in that issuer. The fund or underlying fund is subject to greater levels of credit risk to the extent an underlying fund holds below investment grade debt securities, or “junk” bonds. Market risk is the risk that the fixed income markets may become volatile and less liquid, and the market value of an investment may move up or down, sometimes quickly or unpredictably. Interest rate risk is the risk that the value of a fixed income security will fall when interest rates rise.

Foreign investments and emerging market risk. An underlying fund’s investments in securities of foreign issuers or issuers with significant exposure to foreign markets involve additional risk. Foreign countries in which an underlying fund may invest may have markets that are less liquid, less regulated and more volatile than U.S. markets. The value of an underlying fund’s investments may decline because of factors affecting the particular issuer as well as foreign markets and issuers generally, such as unfavorable or unsuccessful government actions, reduction of government or central bank support and political or financial instability. Lack of information may also affect the value of these securities. To the extent an underlying fund focuses its investments in a single country or only a few countries in a particular geographic region, economic, political, regulatory or other conditions affecting such country or region may have a greater impact on fund performance relative to a more geographically diversified fund.

The risks of foreign investments are heightened when investing in issuers in emerging market countries. Emerging market countries tend to have economic, political and legal systems that are less fully developed and are less stable than those of more developed countries. They are often particularly sensitive to market movements because their market prices tend to reflect speculative expectations. Low trading volumes may result in a lack of liquidity and in extreme price volatility.

Growth and value investing risk. Growth or value securities as a group may be out of favor and underperform the overall equity market while the market concentrates on other types of securities. Growth securities typically are very sensitive to market movements because their market prices tend to reflect future expectations. When it appears those expectations will not be met, the prices of growth securities typically fall. Growth securities may also be more volatile than other investments because they often do not pay dividends. The value approach to investing involves the risk that stocks may remain undervalued. An underlying fund that is growth- or value-oriented may, like many growth or value funds, weight its investments toward certain industries, thus increasing its exposure to factors adversely affecting issuers within those industries and, indirectly, the fund’s exposure to those factors.

Hedge fund strategies risk. The fund, through the underlying funds, may employ investment strategies that involve greater risks than the strategies used by typical mutual funds, including increased use of short sales, leverage and derivative transactions and hedging strategies. The fund may invest in underlying funds employing proprietary investment strategies that are not fully disclosed, which may involve risks that are not anticipated.

High yield (“junk”) bonds risk. High yield bonds are generally subject to greater credit risks than higher-grade bonds, including the risk of default on the payment of interest or principal. High yield bonds are considered speculative, tend to be less liquid and are more difficult to value than higher grade securities. High yield bonds tend to be volatile and more susceptible to adverse events, credit downgrades and negative sentiments and may be difficult to sell at a desired price, or at all, during periods of uncertainty or market turmoil.

Investing in a fund of funds risk. Your cost of investing in the fund, as a fund of funds, may be higher than the cost of investing in a mutual fund that only invests directly in individual equity and fixed income securities. An underlying fund may change its investment objective or policies without the fund’s approval, which could force the fund to withdraw its investment from such underlying fund at a time that is unfavorable to the fund. In addition, one underlying fund may buy the same securities that another underlying fund sells. Therefore, the fund would indirectly bear the costs of these trades without accomplishing any investment purpose. If the fund invests in an underlying fund that has recently commenced operations, there can be no assurance that such underlying fund will grow to or maintain an economically viable size, in which case the underlying fund’s board or adviser may determine to liquidate the underlying fund.

Issuer risk. The value of a security can go up or down more than the market as a whole and can perform differently from the value of the market as a whole, often due to disappointing earnings reports by the issuer, unsuccessful products or services, loss of major customers, major litigation against the issuer or changes in government regulations affecting the issuer or the competitive environment. An underlying fund may experience a substantial or complete loss on an individual security.

Large capitalization company risk. Large capitalization companies may fall out of favor with investors based on market and economic conditions. In return for the relative stability and low volatility of large capitalization companies, an underlying fund’s value may not rise as much as the value of funds that invest in companies with smaller market capitalizations.

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Principal risks cont’d

Liquidity risk. Some assets held by an underlying fund may be impossible or difficult to sell, particularly during times of market turmoil. These illiquid assets may also be difficult to value. Markets may become illiquid when, for instance, there are few, if any, interested buyers or sellers or when dealers are unwilling or unable to make a market for certain securities. As a general matter, dealers recently have been less willing to make markets for fixed income securities. If an underlying fund is forced to sell an illiquid asset to meet redemption requests or other cash needs, the underlying fund may be forced to sell at a loss.

Long/short strategy risk. While an underlying fund may invest in long positions and short positions, there is the risk that the investments will not perform as expected and losses on one type of position could more than offset gains on the other, or the underlying fund could lose money on both positions, if the adviser judges the market incorrectly.

Market events risk. In the past several years financial markets, such as those in the United States, Europe, Asia and elsewhere, have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty. Governmental and non-governmental issuers have defaulted on, or been forced to restructure, their debts. These conditions may continue, recur, worsen or spread. Events that have contributed to these market conditions include, but are not limited to major cybersecurity events; measures to address U.S. federal and state budget deficits; downgrading of U.S. long-term sovereign debt; declines in oil and commodity prices; dramatic changes in currency exchange rates; and public sentiment.

The U.S. government and the Federal Reserve, as well as certain foreign governments and central banks, have taken steps to support financial markets, including by keeping interest rates at historically low levels. This and other government intervention may not work as intended, particularly if the efforts are perceived by investors as being unlikely to achieve the desired results. The Federal Reserve has reduced its market support activities and recently has begun raising interest rates. Certain foreign governments and central banks are implementing or discussing so-called negative interest rates (e.g., charging depositors who keep their cash at a bank) to spur economic growth. Further Federal Reserve or other U.S. or non-U.S. governmental or central bank actions, including interest rate increases or contrary actions by different governments, could negatively affect financial markets generally, increase market volatility and reduce the value and liquidity of securities in which the fund or an underlying fund invests.

Policy and legislative changes in the United States and in other countries are affecting many aspects of financial regulation, and may in some instances contribute to decreased liquidity and increased volatility in the financial markets. The impact of these changes on the markets, and the practical implications for market participants, may not be fully known for some time.

Economies and financial markets throughout the world are increasingly interconnected. Economic, financial or political events, trading and tariff arrangements, terrorism, natural disasters and other circumstances in one country or region could have profound impacts on global economies or markets. As a result, whether or not the fund or an underlying fund invests in securities of issuers located in or with significant exposure to the countries directly affected, the value and liquidity of the fund’s or an underlying fund’s investments may be negatively affected.

Non-diversification risk. The fund is classified as “non-diversified,” which means it may invest a larger percentage of its assets in a smaller number of underlying funds than a diversified fund. To the extent the fund invests its assets in a smaller number of underlying funds, the fund will be more susceptible to negative events affecting those funds than diversified funds. The underlying funds in which the fund invests may be either diversified or non-diversified.

Prepayment or call risk. Many issuers have a right to prepay their securities. If interest rates fall, an issuer may exercise this right. If this happens, an underlying fund will not benefit from the rise in market price that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds at a time when yields on securities available in the market are lower than the yield on the prepaid security. An underlying fund also may lose any premium it paid on the security.

Real assets risk. Investments by the fund in an underlying fund that invests in real assets involve a high degree of risk, including significant financial, operating, and competitive risks. Real assets include properties, natural resources, commodities and infrastructure assets. Investments in underlying funds that invest in real assets expose the fund to adverse macroeconomic conditions, such as a rise in interest rates or a downturn in the economy in which the asset is located, elevating the risk of loss.

Selection risk. The fund’s ability to achieve its investment goal depends upon the portfolio managers’ skill in determining the fund’s strategic asset class allocation and in selecting the best mix of underlying funds. The value of your investment may decrease if the portfolio managers’ judgment about the attractiveness, value or market trends affecting a particular asset class, investment style, underlying fund or other issuer is incorrect.

Small and medium capitalization company risk. An underlying fund will be exposed to additional risks as a result of its investments in the securities of small and medium capitalization companies. Small and medium capitalization companies may fall out of favor with investors; may have limited product lines, operating histories, markets or financial resources; or may be dependent upon a limited management group. The prices of securities of small and medium capitalization companies generally are more volatile than those of large capitalization companies and are more likely to be adversely affected than large capitalization companies by changes in earnings results and investor expectations or poor economic or market conditions, including those experienced during a recession. Securities of small and medium capitalization companies may underperform large

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capitalization companies, may be harder to sell at times and at prices the portfolio managers believe appropriate and may offer greater potential for losses.

Stock market and equity securities risk. The securities markets are volatile and the market prices of the fund’s or an underlying fund’s securities may decline generally. Securities fluctuate in price based on changes in a company’s financial condition and overall market and economic conditions. If the market prices of the securities owned by the fund or an underlying fund fall, the value of your investment in the fund will decline.

Valuation risk. The sales price an underlying fund could receive for any particular portfolio investment may differ from the underlying fund’s valuation of the investment, particularly for securities that trade in thin or volatile markets or that are valued using a fair value methodology. Investors who purchase or redeem fund shares on days when an underlying fund is holding fair-valued securities may receive fewer or more shares or lower or higher redemption proceeds than they would have received if the underlying fund had not fair-valued securities or had used a different valuation methodology. The fund’s and underlying fund’s ability to value their investments may be impacted by technological issues and/or errors by pricing services or other third party service providers.

These risks are discussed in more detail later in this Prospectus or in the SAI.

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Management

Investment manager: Legg Mason Partners Fund Advisor, LLC

Subadviser: QS Investors, LLC (“QS Investors”)

Portfolio managers: Adam J. Petryk, CFA, Thomas Picciochi, CAIA, and Ellen Tesler. Mr. Petryk (Head of Multi-Asset and Solutions of QS Investors) has been a portfolio manager for the fund since June 2016. Mr. Picciochi (Head of Multi-Asset Portfolio Management Implementation of QS Investors) and Ms. Tesler (Portfolio Manager of QS Investors) have been portfolio managers for the fund since May 2014.

Purchase and sale of fund shares

You may purchase, redeem or exchange shares of the fund each day the New York Stock Exchange is open, at the fund’s net asset value determined after receipt of your request in good order, subject to any applicable sales charge.

The fund’s initial and subsequent investment minimums generally are set forth in the accompanying table:

Your Service Agent may impose different investment minimums.

For more information about how to purchase, redeem or exchange shares, and to learn which classes of shares are available to you, you should contact your Service Agent, or, if you hold your shares or plan to purchase shares through the fund, you should contact the fund by phone at 1-877-721-1926, by regular mail at Legg Mason Funds, P.O. Box 9699, Providence, RI 02940-9699 or by express, certified or registered mail at Legg Mason Funds, 4400 Computer Drive, Westborough, MA 01581.

Tax information

The fund’s distributions are generally taxable as ordinary income or capital gain.

Payments to broker/dealers and other financial intermediaries

The fund’s related companies may pay Service Agents for the sale of fund shares, shareholder services and other purposes. These payments create a conflict of interest by influencing your Service Agent or its employees or associated persons to recommend the fund over another investment. Ask your financial adviser or salesperson or visit your Service Agents’s or salesperson’s website for more information.

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QS Defensive Growth Fund

Investment objective

The fund seeks income as a primary objective and long-term growth of capital as a secondary objective.

Fees and expenses of the fund

The accompanying table describes the fees and expenses that you may pay if you buy and hold shares of the fund.

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in funds sold by Legg Mason Investor Services, LLC (“LMIS”), the fund’s distributor. More information about these and other discounts is available from your Service Agent, in this Prospectus on page 56 under the heading “Sales charges,” in the appendix titled “Appendix: Waivers and Discounts Available from Certain Service Agents” on page 91 of this Prospectus and in the fund’s statement of additional information (“SAI”) on page 74 under the heading “Sales Charge Waivers and Reductions for Class A Shares.” “Service Agents” include banks, brokers, dealers, insurance companies, investment advisers, financial consultants or advisers, mutual fund supermarkets and other financial intermediaries that have entered into an agreement with LMIS to sell shares of the fund.

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Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes:

Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover. The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 18% of the average value of its portfolio.

Principal investment strategies

The fund is a fund of funds—it invests in other mutual funds and ETFs. The fund is managed as an asset allocation program and allocates its assets among funds and ETFs managed by the manager and its affiliates and ETFs managed by unaffiliated investment advisers (underlying funds). The fund’s ability to invest in ETFs—whether managed by the manager or its affiliates or by unaffiliated investment advisers—will be effective as of July 1, 2017. After July 1, 2017, the portfolio managers will be able to allocate investments among underlying funds that are mutual funds and ETFs.

The fund organizes its investments in underlying funds into two main asset classes: the equity class (equity securities of all types) and the fixed income class (fixed income securities of all types). The portfolio managers may invest across all asset classes and strategies. The portfolio managers will allocate between 15% to 45% of the fund’s assets to underlying funds that invest in equity and equity-like strategies and between 55% to 85% of the fund’s assets to underlying funds that invest in fixed income strategies. The portfolio managers may, however, allocate fund assets to any underlying funds in varying amounts in a manner consistent with the fund’s investment objective. The fund’s allocation to each class will be measured at the time of purchase and may vary thereafter as a result of market movements.

The portfolio managers will seek to maintain a level of risk in the fund similar to that of the fund’s composite benchmark as defined under “Performance” below.

The underlying funds have a range of investment styles and focuses. The underlying funds may invest in foreign and emerging markets and engage in derivative transactions. The underlying equity funds may include exposure to any market cap or investment style including alternative investments (such as commodities, real estate assets and infrastructure assets). The underlying equity funds may employ strategies similar to those used by hedge funds, which may have a low correlation to broad stock market movements or take both long and short positions in equity securities. The underlying fixed income funds include funds investing in any sector, region or style, including foreign fixed income strategies, currency strategies,

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Principal investment strategies cont’d

inflation-indexed securities, structured credit and distressed debt. The underlying funds may take both long and short positions in fixed income securities. Such funds may also seek to profit from changes in global financial markets and take positions to take advantage of changes in interest rates, exchange rates, liquidity and other macroeconomic factors. The fixed income funds may also invest in securities having maturities of any length and any credit quality, including securities rated below investment grade (commonly known as “junk “bonds). The portfolio managers may invest the fund’s assets in underlying funds that have a limited performance history.

Principal risks

Risk is inherent in all investing. The value of your investment in the fund, as well as the amount of return you receive on your investment, may fluctuate significantly. You may lose part or all of your investment in the fund or your investment may not perform as well as other similar investments. The following is a summary description of certain risks of investing in the fund.

Affiliated funds risk. The fund’s manager serves as manager of the underlying Legg Mason funds and ETFs and Western Asset funds and is affiliated with the manager of the underlying Royce funds. In addition, the fund may invest in certain underlying funds (including ETFs) for which the fund’s subadviser serves as adviser. It is possible that a conflict of interest among the fund and the underlying funds could affect how the fund’s manager and subadviser fulfill their fiduciary duties to the fund and the underlying funds. For example, the subadviser may have an incentive to allocate the fund’s assets to those funds for which the fees paid to the manager or subadviser are higher than the fees paid by other underlying funds or to those funds for which the subadviser serves as adviser. However, the fund’s Board of Trustees believes the fund has been structured to mitigate these concerns.

Asset class variation risk. The underlying funds invest principally in the securities constituting their asset class ( i.e. , equity or fixed income). However, under normal market conditions, an underlying fund may vary the percentage of its assets in these securities (subject to any applicable regulatory requirements).

Credit risk. If an issuer or guarantor of a security held by an underlying fund or a counterparty to a financial contract with an underlying fund defaults or is downgraded, or is perceived to be less creditworthy, or if the value of the assets underlying a security declines, the value of your investment will typically decline. Subordinated securities are more likely to suffer a credit loss than non-subordinated securities of the same issuer and will be disproportionately affected by a default, downgrade or perceived decline in creditworthiness.

Currency risk. The value of investments in securities denominated in foreign currencies increases or decreases as the rates of exchange between those currencies and the U.S. dollar change. Currency conversion costs and currency fluctuations could erase investment gains or add to investment losses. Currency exchange rates can be volatile, and are affected by factors such as general economic conditions, the actions of the U.S. and foreign governments or central banks, the imposition of currency controls and speculation.

Cybersecurity risk. Cybersecurity incidents may allow an unauthorized party to gain access to fund assets, customer data (including private shareholder information), or proprietary information, or cause the fund, the manager, the subadvisers and/or their service providers (including, but not limited to, fund accountants, custodians, sub-custodians, transfer agents and financial intermediaries) to suffer data breaches, data corruption or lose operational functionality.

Derivatives risk. Using derivatives can increase an underlying fund’s losses and reduce opportunities for gains when market prices, interest rates, currencies or the derivatives themselves, behave in a way not anticipated by the underlying fund. Using derivatives also can have a leveraging effect and increase fund volatility. Certain derivatives have the potential for unlimited loss, regardless of the size of the initial investment. Derivatives may be difficult to sell, unwind or value, and the counterparty may default on its obligations to the underlying fund. Derivatives are generally subject to the risks applicable to the assets, rates, indices or other indicators underlying the derivative. The value of a derivative may fluctuate more than the underlying assets, rates, indices or other indicators to which it relates. Use of derivatives may have different tax consequences for an underlying fund than an investment in the underlying security, and those differences may affect the amount, timing and character of income distributed to shareholders. The U.S. government and foreign governments are in the process of adopting and implementing regulations governing derivatives markets, including mandatory clearing of certain derivatives, margin and reporting requirements. The ultimate impact of the regulations remains unclear. Additional regulation of derivatives may make derivatives more costly, limit their availability or utility, otherwise adversely affect their performance or disrupt markets. In addition, the SEC has proposed a new rule that would change the regulation of the use of derivatives by registered investment companies, such as an underlying fund. If the proposed rule takes effect, it could limit the ability of an underlying fund to invest in derivatives.

Credit default swap contracts involve heightened risks and may result in losses to an underlying fund. Credit default swaps may be illiquid and difficult to value, and they increase credit risk since the underlying fund has exposure to both the issuer whose credit is the subject of the swap and the counterparty to the swap.

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ETFs risk. Investing in an ETF will give the fund exposure to the securities comprising the index on which the ETF is based and will expose the fund to risks similar to those of investing directly in those securities. Shares of ETFs are traded on an exchange and may trade at either a premium or discount to net asset value. The fund will pay brokerage commissions in connection with the purchase and sale of shares of ETFs.

Extension risk. If interest rates rise, repayments of fixed income securities may occur more slowly than anticipated by the market. This may drive the prices of these securities down because their interest rates are lower than the current interest rate and they remain outstanding longer.

Fixed income securities risk. Fixed income securities are subject to a number of risks, including credit, market and interest rate risks. Credit risk is the risk that the issuer or obligor will not make timely payments of principal and interest. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of an underlying fund’s investment in that issuer. The fund or underlying fund is subject to greater levels of credit risk to the extent an underlying fund holds below investment grade debt securities, or “junk” bonds. Market risk is the risk that the fixed income markets may become volatile and less liquid, and the market value of an investment may move up or down, sometimes quickly or unpredictably. Interest rate risk is the risk that the value of a fixed income security will fall when interest rates rise.

Foreign investments and emerging market risk. An underlying fund’s investments in securities of foreign issuers or issuers with significant exposure to foreign markets involve additional risk. Foreign countries in which an underlying fund may invest may have markets that are less liquid, less regulated and more volatile than U.S. markets. The value of an underlying fund’s investments may decline because of factors affecting the particular issuer as well as foreign markets and issuers generally, such as unfavorable or unsuccessful government actions, reduction of government or central bank support and political or financial instability. Lack of information may also affect the value of these securities. To the extent an underlying fund focuses its investments in a single country or only a few countries in a particular geographic region, economic, political, regulatory or other conditions affecting such country or region may have a greater impact on fund performance relative to a more geographically diversified fund.

The risks of foreign investments are heightened when investing in issuers in emerging market countries. Emerging market countries tend to have economic, political and legal systems that are less fully developed and are less stable than those of more developed countries. They are often particularly sensitive to market movements because their market prices tend to reflect speculative expectations. Low trading volumes may result in a lack of liquidity and in extreme price volatility.

Growth and value investing risk. Growth or value securities as a group may be out of favor and underperform the overall equity market while the market concentrates on other types of securities. Growth securities typically are very sensitive to market movements because their market prices tend to reflect future expectations. When it appears those expectations will not be met, the prices of growth securities typically fall. Growth securities may also be more volatile than other investments because they often do not pay dividends. The value approach to investing involves the risk that stocks may remain undervalued. An underlying fund that is growth- or value-oriented may, like many growth or value funds, weight its investments toward certain industries, thus increasing its exposure to factors adversely affecting issuers within those industries and, indirectly, the fund’s exposure to those factors.

Hedge fund strategies risk. The fund, through the underlying funds, may employ investment strategies that involve greater risks than the strategies used by typical mutual funds, including increased use of short sales, leverage and derivative transactions and hedging strategies. The fund may invest in underlying funds employing proprietary investment strategies that are not fully disclosed, which may involve risks that are not anticipated.

High yield (“junk”) bonds risk. High yield bonds are generally subject to greater credit risks than higher-grade bonds, including the risk of default on the payment of interest or principal. High yield bonds are considered speculative, tend to be less liquid and are more difficult to value than higher grade securities. High yield bonds tend to be volatile and more susceptible to adverse events, credit downgrades and negative sentiments and may be difficult to sell at a desired price, or at all, during periods of uncertainty or market turmoil.

Investing in a fund of funds risk. Your cost of investing in the fund, as a fund of funds, may be higher than the cost of investing in a mutual fund that only invests directly in individual equity and fixed income securities. An underlying fund may change its investment objective or policies without the fund’s approval, which could force the fund to withdraw its investment from such underlying fund at a time that is unfavorable to the fund. In addition, one underlying fund may buy the same securities that another underlying fund sells. Therefore, the fund would indirectly bear the costs of these trades without accomplishing any investment purpose. If the fund invests in an underlying fund that has recently commenced operations, there can be no assurance that such underlying fund will grow to or maintain an economically viable size, in which case the underlying fund’s board or adviser may determine to liquidate the underlying fund.

Issuer risk. The value of a security can go up or down more than the market as a whole and can perform differently from the value of the market as a whole, often due to disappointing earnings reports by the issuer, unsuccessful products or services, loss of major customers, major litigation against the issuer or changes in government regulations affecting the issuer or the competitive environment. An underlying fund may experience a substantial or complete loss on an individual security.

Large capitalization company risk. Large capitalization companies may fall out of favor with investors based on market and economic conditions. In return for the relative stability and low volatility of large capitalization companies, an underlying fund’s value may not rise as much as the value of funds that invest in companies with smaller market capitalizations.

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Principal risks cont’d

Liquidity risk. Some assets held by an underlying fund may be impossible or difficult to sell, particularly during times of market turmoil. These illiquid assets may also be difficult to value. Markets may become illiquid when, for instance, there are few, if any, interested buyers or sellers or when dealers are unwilling or unable to make a market for certain securities. As a general matter, dealers recently have been less willing to make markets for fixed income securities. If an underlying fund is forced to sell an illiquid asset to meet redemption requests or other cash needs, the underlying fund may be forced to sell at a loss.

Long/short strategy risk. While an underlying fund may invest in long positions and short positions, there is the risk that the investments will not perform as expected and losses on one type of position could more than offset gains on the other, or the underlying fund could lose money on both positions, if the adviser judges the market incorrectly.

Market events risk. In the past several years financial markets, such as those in the United States, Europe, Asia and elsewhere, have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty. Governmental and non-governmental issuers have defaulted on, or been forced to restructure, their debts. These conditions may continue, recur, worsen or spread. Events that have contributed to these market conditions include, but are not limited to major cybersecurity events; measures to address U.S. federal and state budget deficits; downgrading of U.S. long-term sovereign debt; declines in oil and commodity prices; dramatic changes in currency exchange rates; and public sentiment.

The U.S. government and the Federal Reserve, as well as certain foreign governments and central banks, have taken steps to support financial markets, including by keeping interest rates at historically low levels. This and other government intervention may not work as intended, particularly if the efforts are perceived by investors as being unlikely to achieve the desired results. The Federal Reserve has reduced its market support activities and recently has begun raising interest rates. Certain foreign governments and central banks are implementing or discussing so-called negative interest rates (e.g., charging depositors who keep their cash at a bank) to spur economic growth. Further Federal Reserve or other U.S. or non-U.S. governmental or central bank actions, including interest rate increases or contrary actions by different governments, could negatively affect financial markets generally, increase market volatility and reduce the value and liquidity of securities in which the fund or an underlying fund invests.

Policy and legislative changes in the United States and in other countries are affecting many aspects of financial regulation, and may in some instances contribute to decreased liquidity and increased volatility in the financial markets. The impact of these changes on the markets, and the practical implications for market participants, may not be fully known for some time.

Economies and financial markets throughout the world are increasingly interconnected. Economic, financial, or political events, trading and tariff arrangements, terrorism, natural disasters and other circumstances in one country or region could have profound impacts on global economies or markets. As a result, whether or not the fund or an underlying fund invests in securities of issuers located in or with significant exposure to the countries directly affected, the value and liquidity of the fund’s or underlying fund’s investments may be negatively affected.

Non-diversification risk. The fund is classified as “non-diversified,” which means it may invest a larger percentage of its assets in a smaller number of underlying funds than a diversified fund. To the extent the fund invests its assets in a smaller number of underlying funds, the fund will be more susceptible to negative events affecting those funds than diversified funds. The underlying funds in which the fund invests may be either diversified or non-diversified.

Prepayment or call risk. Many issuers have a right to prepay their securities. If interest rates fall, an issuer may exercise this right. If this happens, an underlying fund will not benefit from the rise in market price that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds at a time when yields on securities available in the market are lower than the yield on the prepaid security. An underlying fund also may lose any premium it paid on the security.

Real assets risk. Investments by the fund in an underlying fund that invests in real assets involve a high degree of risk, including significant financial, operating, and competitive risks. Real assets include properties, natural resources, commodities and infrastructure assets. Investments in underlying funds that invest in real assets expose the fund to adverse macroeconomic conditions, such as a rise in interest rates or a downturn in the economy in which the asset is located, elevating the risk of loss.

Selection risk. The fund’s ability to achieve its investment goal depends upon the portfolio managers’ skill in determining the fund’s strategic asset class allocation and in selecting the best mix of underlying funds. The value of your investment may decrease if the portfolio managers’ judgment about the attractiveness, value or market trends affecting a particular asset class, investment style, underlying fund or other issuer is incorrect.

Small and medium capitalization company risk. An underlying fund will be exposed to additional risks as a result of its investments in the securities of small and medium capitalization companies. Small and medium capitalization companies may fall out of favor with investors; may have limited product lines, operating histories, markets or financial resources; or may be dependent upon a limited management group. The prices of securities of small and medium capitalization companies generally are more volatile than those of large capitalization companies and are more likely to be adversely affected than large capitalization companies by changes in earnings results and investor expectations or poor economic or market conditions, including those experienced during a recession. Securities of small and medium capitalization companies may underperform large

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capitalization companies, may be harder to sell at times and at prices the portfolio managers believe appropriate and may offer greater potential for losses.

Stock market and equity securities risk. The securities markets are volatile and the market prices of the fund’s or an underlying fund’s securities may decline generally. Securities fluctuate in price based on changes in a company’s financial condition and overall market and economic conditions. If the market prices of the securities owned by the fund or an underlying fund fall, the value of your investment in the fund will decline.

Valuation risk. The sales price an underlying fund could receive for any particular portfolio investment may differ from the underlying fund’s valuation of the investment, particularly for securities that trade in thin or volatile markets or that are valued using a fair value methodology. Investors who purchase or redeem fund shares on days when an underlying fund is holding fair-valued securities may receive fewer or more shares or lower or higher redemption proceeds than they would have received if the underlying fund had not fair-valued securities or had used a different valuation methodology. The fund’s and underlying fund’s ability to value their investments may be impacted by technological issues and/or errors by pricing services or other third party service providers.

These risks are discussed in more detail later in this Prospectus or in the SAI.

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Management

Investment manager: Legg Mason Partners Fund Advisor, LLC

Subadviser: QS Investors, LLC (“QS Investors”)

Portfolio managers: Adam J. Petryk, CFA, Thomas Picciochi, CAIA, and Ellen Tesler. Mr. Petryk (Head of Multi-Asset and Solutions of QS Investors) has been a portfolio manager for the fund since June 2016. Mr. Picciochi (Head of Multi-Asset Portfolio Management Implementation of QS Investors) and Ms. Tesler (Portfolio Manager of QS Investors) have been portfolio managers for the fund since May 2014.

Purchase and sale of fund shares

You may purchase, redeem or exchange shares of the fund each day the New York Stock Exchange is open, at the fund’s net asset value determined after receipt of your request in good order, subject to any applicable sales charge.

The fund’s initial and subsequent investment minimums generally are set forth in the accompanying table: