November 28, 2012

Summary

Prospectus

Western Asset

Short Term

Yield Fund

Class : Ticker Symbol

FI : —

I : WTYIX

IS: —

Before you invest, you may want to review the fund’s Prospectus, which contains more information about the fund and its risks. You can find the fund’s Prospectus and other information about the fund, including the fund’s statement of additional information and shareholder reports, online at http://www.leggmason.com/individualinvestors/prospectuses (click on the name of the fund). You can also get this information at no cost by calling the fund at 1-877-721-1926 or by sending an
e-mail request to prospectus@leggmason.com, or from your financial intermediary. The fund’s Prospectus, dated November 28, 2012 and as may be amended or supplemented and the fund’s statement of additional information, dated November 28, 2012 and as may be amended or supplemented are incorporated by reference into this Summary Prospectus.

INVESTMENT PRODUCTS: NOT FDIC INSURED • NO BANK GUARANTEE • MAY LOSE VALUE

Investment objective

The fund seeks current 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.

Shareholder fees (fees paid directly from your investment)
	Class FI	Class I	Class IS
Maximum sales charge (load) imposed on purchases	None	None	None
Maximum deferred sales charge (load)	None	None	None
Annual fund operating expenses (expenses that you pay each year as a percentage of the value of your investment) (%)
	Class FI	Class I	Class IS
Management fees	0.25	0.25	0.25
Distribution and service (12b-1) fees	0.25	None	None
Other expenses1	0.46	0.36	0.26
Total annual fund operating expenses	0.96	0.61	0.51
Fees waived and/or expenses reimbursed2	(0.26)	(0.16)	(0.16)
Total annual fund operating expenses after waiving fees and/or reimbursing expenses	0.70	0.45	0.35

¹  “Other expenses” for Class FI shares, Class I shares and Class IS shares are estimated for the current fiscal year. Actual expenses may differ from estimates.

²  The manager has agreed to waive fees and/or reimburse operating expenses (other than interest, brokerage, taxes, extraordinary expenses and acquired fund fees and expenses) so that total annual operating expenses are not expected to exceed 0.70% for Class FI shares, 0.45% for Class I shares and 0.35% for Class IS shares. These arrangements cannot be terminated prior to December 31, 2014 without the Board of Trustees’ consent. The manager is permitted to recapture amounts waived and/or reimbursed to a class during the same fiscal year if the class’ total annual operating expenses have fallen to a level below the limits described above.

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:

Ÿ You invest $10,000 in the fund for the time periods indicated

Ÿ Your investment has a 5% return each year and the fund’s operating expenses remain the same

Ÿ You reinvest all distributions and dividends without a sales charge

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

Number of years you own your shares ($)	1 year	3 years
Class FI	72	280
Class I	46	179
Class IS	36	148

The fund invests in securities through an underlying fund: Short Term Yield Portfolio. The information above reflects the direct expenses of the fund and its allocated share of expenses of Short Term Yield Portfolio.

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. The fund is newly offered; therefore, it does not have a turnover rate to report for the most recent fiscal year.

Principal investment strategies

The fund invests in U.S. dollar denominated investment grade fixed income securities, including corporate debt securities, bank obligations, commercial paper, asset-backed and mortgage-backed securities, structured instruments and securities issued by the U.S. government and its agencies and instrumentalities, U.S. states and municipalities, or foreign governments. Foreign securities will generally be limited to issuers, including banks, corporations and foreign governments, located in the major industrialized countries.

The fund is not a money market fund and does not seek to maintain a stable net asset value of $1.00 per share.

Under normal circumstances, the effective duration of the fund’s portfolio, as estimated by the subadviser, is expected to be one year or less. Duration is a measure of the underlying portfolio’s price sensitivity to changes in prevailing interest rates. The assumptions that are made about a security’s features and options when calculating effective duration may prove to be incorrect. As a result, investors should be aware that effective duration is not an exact measurement and may not reliably predict a security’s price sensitivity to changes in yield or interest rates.

The fund expects to maintain a dollar-weighted average effective maturity of not more than 18 months, but in any event will maintain a dollar weighted average effective maturity of not more than three years. The “average effective portfolio maturity” of the fund is a weighted average of all the maturities of the securities in the portfolio, computed by weighting each security’s effective maturity, as estimated by the subadviser, by the market value of the security. For the purposes of determining the fund’s average effective maturity, a security’s maturity date will generally be deemed to be the next interest rate reset date for an adjustable rate security or, if earlier, the date of the next demand feature such as a put feature, when the fund would be entitled to receive payment of principal and interest. The subadviser may also take into account estimated future prepayments on securities, such as mortgage-backed securities, with uncertain future cash flows and estimations of call features and similar features and options. These estimates may prove to be incorrect.

In addition, the fund will not purchase a security if, at the time of purchase, the security has a remaining final maturity, taking into account demand features, but without taking into account any interest reset provisions, of more than five years, or, with respect to asset- or mortgage-backed securities, an average life of more than five years. Average life refers to the weighted average of the times at which principal repayments are expected to be fully repaid.

The fund invests only in securities that, at the time of purchase, are rated in one of the top three rating categories (which may include gradations within each category) or the equivalent short term rating by one or more rating agencies followed by the fund or, if unrated, are judged by the subadviser to be of comparable quality.

The fund may use instruments such as derivatives, including futures and option contracts, and synthetic instruments. The fund may use one or more types of these instruments without limit. The fund is permitted to engage in a variety of transactions using derivatives, but only for hedging purposes. For additional information regarding derivatives, see “More on the fund’s investment strategies, investments and risks—Derivatives” in the fund’s Prospectus.

Certain risks

Risk is inherent in all investing. There is no assurance that the fund will meet its investment objective. 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.

Market and interest rate risk. The market prices of the fund’s securities may go up or down, sometimes rapidly or unpredictably, due to general market conditions, such as real or perceived adverse economic or political conditions, inflation, changes in interest rates, lack of liquidity in the bond markets or adverse investor sentiment. When market prices fall, the value of your investment will go down. The value of your investment may also go down when interest rates rise. A rise in rates tends to have a greater impact on the prices of longer term or duration securities. The financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities of issuers worldwide. Some governmental and non-governmental issuers (notably in Europe) have defaulted on, or been forced to restructure, their debts, and many other issuers have faced difficulties obtaining credit. These market conditions may continue, worsen or spread, including in the United States, Europe and beyond. Further defaults or

restructurings by governments and others of their debt could have additional adverse effects on economies, financial markets and asset valuations around the world. In response to the crisis, the U.S. and other governments and the Federal Reserve and certain foreign central banks have taken steps to support financial markets. The withdrawal of this support, failure of efforts in response to the crisis, or investor perception that these efforts are not succeeding could negatively affect financial markets generally as well as the value and liquidity of certain securities. Whether or not the fund invests in securities of issuers located in or with significant exposure to countries experiencing economic and financial difficulties, the value and liquidity of the fund’s investments may be negatively affected by the conditions in the countries experiencing the difficulties. In addition, policy and legislative changes in the United States and in other countries are changing many aspects of financial regulation. The impact of these changes on the markets, and the practical implications for market participants, may not be fully known for some time.

Credit risk. If an issuer or guarantor of a security held by the fund or a counterparty to a financial contract with the 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.

Derivatives risk. Using derivatives can increase fund losses and reduce opportunities for gains when market prices, interest rates or the derivative instruments themselves behave in a way not anticipated by the fund. Using derivatives also can have a leveraging effect and increase fund volatility. Derivatives may be difficult to sell, unwind or value, and the counterparty may default on its obligations to the fund. Recent legislation calls for new regulation of the derivatives markets. The extent and impact of the regulation are not yet fully known and may not be for some time. New regulation of derivatives may make them more costly, may limit their availability, or may otherwise adversely affect their value or performance.

Leveraging risk. The value of your investment may be more volatile if the fund borrows or uses derivatives or other investments that have a leveraging effect on the fund’s portfolio. Other risks also will be compounded. This is because leverage generally magnifies the effect of a change in the value of an asset and creates a risk of loss of value on a larger pool of assets than the fund would otherwise have had, potentially resulting in the loss of all assets. The fund may also have to sell assets at inopportune times to satisfy its obligations.

Liquidity risk. Some securities held by the fund may be difficult to sell, or illiquid, particularly during times of market turmoil. Illiquid securities may also be difficult to value. If the fund is forced to sell an illiquid asset to meet redemption requests or other cash needs, the fund may be forced to sell at a loss.

Foreign investments risk. The fund’s investments in securities of foreign issuers or issuers with significant exposure to foreign markets involve additional risk. Foreign countries in which the fund may invest may have markets that are less liquid, less regulated and more volatile than U.S. markets. The value of the fund’s investments may decline because of factors affecting the particular issuer as well as foreign markets and issuers generally, such as unfavorable government actions, and political or financial instability. Lack of information may also affect the value of these securities.

Risk of increase in expenses. Your actual costs of investing in the fund may be higher than the expenses shown in “Annual fund operating expenses” for a variety of reasons. For example, expense ratios may be higher than those shown if a fee limitation is changed or terminated or if average net assets are lower than estimated. Net assets are more likely to decrease and fund expense ratios are more likely to increase when markets are volatile.

Structured securities risk. The payment and credit qualities of structured securities derive from their underlying assets, and they may behave in ways not anticipated by the fund, or they may not receive tax, accounting or regulatory treatment anticipated by the fund.

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, the fund 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. The fund also may lose any premium it paid on the security.

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.

Valuation risk. The sales price the fund could receive for any particular portfolio investment may differ from the 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 the 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 fund had not fair-valued the security or had used a different valuation methodology.

Risk of investing in fewer issuers. To the extent the fund invests its assets in a small number of issuers, the fund will be more susceptible to negative events affecting those issuers.

Portfolio turnover risk. Active and frequent trading may increase a shareholder’s tax liability and transaction costs, which could detract from fund performance.

Portfolio selection risk. The value of your investment may decrease if the subadviser’s judgment about the quality, relative yield, value or market trends affecting a particular security, industry or sector, or about interest rates, is incorrect.

Not a money market fund. The fund is not a money market fund and is not subject to the strict rules that govern the quality, maturity, liquidity and other features of securities that money market funds may purchase. Under normal conditions, the fund’s investment may be more susceptible than a money market fund to interest rate risk, valuation risk, credit risk and other risks relevant to the fund’s investments. The fund does not attempt to maintain a stable net asset value. Therefore, the fund’s net asset value per share will fluctuate.

These risks are discussed in more detail in the fund’s Prospectus or in the Statement of Additional Information (“SAI”).

Performance

The fund is newly offered. Once the fund has a performance record of at least one calendar year, the fund’s performance will be included in its Prospectus. The fund makes updated performance information available at the fund’s website, http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class), or by calling the fund at 1-877-721-1926.

Management

Investment manager: Legg Mason Partners Fund Advisor, LLC

Subadviser: Western Asset Management Company

Investment professionals: Stephen A. Walsh, Kevin K. Kennedy and Martin R. Hanley. Messrs. Walsh, Kennedy and Hanley have been a part of the portfolio management team for the fund since the fund’s inception. These investment professionals work together with a broader investment management team.

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.

The fund’s initial and subsequent investment minimums generally are as follows:

Investment minimum initial/additional investment ($)
	Class FI	Class I	Class IS
General	N/A	1 million/None*	N/A
Uniform Gifts or Transfers to Minor Accounts	N/A	1 million/None*	N/A
IRAs	N/A	1 million/None*	N/A
SIMPLE IRAs	N/A	1 million/None*	N/A
Systematic Investment Plans	N/A	1 million/None*	N/A
Clients of Eligible Financial Intermediaries	None/None	None/None	N/A
Eligible Investment Programs	None/None	None/None	N/A
Retirement Plans with omnibus accounts held on the books of the fund and certain rollover IRAs	None/None	None/None	None/None
Other Retirement Plans	N/A	1 million/None*	N/A
Institutional Investors	N/A	1 million/None	1 million/None

* Available to investors investing directly with the fund.

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 or by mail at Legg Mason Funds, P.O. Box 55214, Boston, MA 02205-8504.

Tax information

The fund intends to make distributions that may be taxed as ordinary income or capital gains.

Payments to broker/dealers and other financial intermediaries

The fund’s related companies may pay broker/dealers or other financial intermediaries (such as a bank or an insurance company) for the sale of fund shares and related services. These payments create a conflict of interest by influencing your broker/dealer or other intermediary 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.

WASX013626SP 11/12