Western Asset Investment Grade Defined Opportunity Trust (IGI) SC TO-IIssuer tender offer statement

Exhibit (a)(1)(iii)

OFFER BY

WESTERN ASSET INVESTMENT GRADE DEFINED OPPORTUNITY TRUST INC.

TO PURCHASE FOR CASH

UP TO 100% OF THE FUND’S OUTSTANDING

SHARES OF COMMON STOCK

AT 100% OF NET ASSET VALUE PER SHARE

THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 5:00 P.M.,

NEW YORK CITY TIME, ON OCTOBER 1, 2024 OR SUCH LATER DATE

TO WHICH THE OFFER IS EXTENDED (“TERMINATION DATE”)

THIS OFFER IS NOT CONDITIONED ON ANY MINIMUM NUMBER OF SHARES BEING

TENDERED, BUT IS SUBJECT TO OTHER CONDITIONS AS OUTLINED IN THE FUND’S

OFFER TO PURCHASE AND IN THE LETTER OF TRANSMITTAL.

September 3, 2024

Trust Companies and Other Nominees:

We are enclosing herewith the material listed below relating to the offer of Western Asset Investment Grade Defined Opportunity Trust Inc., a Maryland corporation registered under the Investment Company Act of 1940, as amended, as a closed-end, non-diversified management investment company (the “Fund”), to purchase up to 100% of the Fund’s outstanding shares of common stock (the “Shares”), upon the terms and conditions set forth in its Offer to Purchase dated September 3, 2024 and in the related Letter of Transmittal (which together constitute the “Offer”). The price to be paid for the Shares is an amount per Share, equal to 100% of the net asset value per Share as determined by the Fund at the close of regular trading session on the New York Stock Exchange on October 1, 2024, or if the Offer is extended, on the next trading day after the day to which the Tender Offer is extended. Following the Offer, if less than $50 million of net assets remain in the Fund, the Offer will be cancelled and the Fund will liquidate on or about December 2, 2024.

We are asking you to contact your clients for whom you hold Shares registered in your name (or in the name of your nominee) or who hold Shares registered in their own names. Please bring the Offer to their attention as promptly as possible. No fees or commission will be payable to the Fund in connection with the Offer. However, brokers, dealers or other persons may charge Stockholders a fee for soliciting tenders for Shares pursuant to the Offer. The Fund will also, upon request, reimburse you for reasonable and customary mailing and handling expenses incurred by you in forwarding any of the enclosed materials to your clients. The Fund will pay all transfer taxes on its purchase of Shares, subject to Instruction 6, “Stock Transfer Taxes,” of the Letter of Transmittal. However, backup withholding at a 24% rate may be required unless either an exemption is established or the required taxpayer identification number (in the case of U.S. Stockholders) and certifications are provided. In addition, in the case of non-U.S. Stockholders, 30% (or lower treaty rate) withholding at the source or under the Foreign Account Tax Compliance Act may be required unless an exemption from or reduction of such withholding is established. See Section 3 of the Offer to Purchase.

For your information and for forwarding to your clients, we are enclosing the following documents:

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Exhibit (a)(1)(iii)

The Offer is not being made to, nor will the Fund accept tenders from, holders of Shares in any state or other jurisdiction in which the Offer would not be in compliance with the securities or Blue Sky laws of such jurisdiction.

None of the Fund, its Board of Directors or the Fund’s investment manager or subadviser makes any recommendation to any Stockholder whether to tender or not to tender any Shares.

Additional copies of the enclosed material may be obtained from the Information Agent at the appropriate address and telephone number set forth in the Fund’s Offer to Purchase. Any questions you have with respect to the Offer should be directed to the Information Agent at its address and telephone numbers set forth in the Offer to Purchase.

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