SCHEDULE 13D/A 0000921895-24-001846 0001559771 XXXXXXXX LIVE 4 Class A Common Stock, $0.01 par value per share 09/11/2025 false 0001871509 73642K106 Portillo's Inc.

C/O THE PORTILLO RESTAURANT GROUP 2001 SPRING ROAD, SUITE 400 OAK BROOK IL 60523-1903

GLENN W. WELLING 949-734-7900 ENGAGED CAPITAL, LLC 610 Newport Center Drive, Suite 950 Newport Beach CA 92660 RYAN NEBEL 212-451-2300 OLSHAN FROME WOLOSKY LLP 1325 Avenue of the Americas New York NY 10019 0001580761 N Engaged Capital Flagship Master Fund, LP WC N E9 0.00 3534411.00 0.00 3534411.00 3534411.00 N 4.9 PN 0002026762 N Engaged Capital Co-Invest XVII, LP WC N DE 0.00 1534890.00 0.00 1534890.00 1534890.00 N 2.1 PN 0001559771 N Engaged Capital LLC OO N DE 0.00 5069301.00 0.00 5069301.00 5069301.00 N 7.0 IA OO 0001580769 N Engaged Capital Holdings, LLC OO N DE 0.00 5069301.00 0.00 5069301.00 5069301.00 N 7.0 OO 0001580771 N Welling Glenn W. OO N X1 0.00 5069301.00 0.00 5069301.00 5069301.00 N 7.0 IN Class A Common Stock, $0.01 par value per share Portillo's Inc. C/O THE PORTILLO RESTAURANT GROUP 2001 SPRING ROAD, SUITE 400 OAK BROOK IL 60523-1903 Item 3 is hereby amended and restated to read as follows: The Shares purchased by Engaged Capital Flagship Master and Engaged Capital Co-Invest XVII were purchased with working capital (which may, at any given time, include margin loans made by brokerage firms in the ordinary course of business). The aggregate purchase price of the 3,534,411 Shares beneficially owned by Engaged Capital Flagship Master is approximately $38,757,991, including brokerage commissions. The aggregate purchase price of the 1,534,890 Shares beneficially owned by Engaged Capital Co-Invest XVII is approximately $16,712,391, including brokerage commissions. Item 4 is hereby amended to add the following: The Reporting Persons have engaged, and intend to continue to engage, in discussions with the Board of the Issuer in accordance with the terms of the Cooperation Agreement. Item 5(a) is hereby amended and restated to read as follows: The aggregate percentage of Shares reported owned by each person named herein is based upon 71,905,580 Shares outstanding as of July 29, 2025, which is the total number of Shares outstanding as reported in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on August 5, 2025. As of the date hereof, Engaged Capital Flagship Master directly beneficially owned 3,534,411 Shares, constituting approximately 4.9% of the Shares outstanding. As of the date hereof, Engaged Capital Co-Invest XVII directly beneficially owned 1,534,890 Shares, constituting approximately 2.1% of the Shares outstanding. Engaged Capital, as the general partner and investment adviser of each of Engaged Capital Flagship Master and Engaged Capital Co-Invest XVII, may be deemed to beneficially own the 5,069,301 Shares owned in the aggregate by Engaged Capital Flagship Master and Engaged Capital Co-Invest XVII, constituting approximately 7.0% of the Shares outstanding. Engaged Holdings, as the managing member of Engaged Capital, may be deemed to beneficially own the 5,069,301 Shares owned in the aggregate by Engaged Capital Flagship Master and Engaged Capital Co-Invest XVII, constituting approximately 7.0% of the Shares outstanding. Mr. Welling, as the Founder and CIO of Engaged Capital and sole member of Engaged Holdings, may be deemed to beneficially own the 5,069,301 Shares owned in the aggregate by Engaged Capital Flagship Master and Engaged Capital Co-Invest XVII, constituting approximately 7.0% of the Shares outstanding. The filing of this Schedule 13D shall not be deemed an admission that the Reporting Persons are, for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, the beneficial owners of any securities of the Issuer he or it does not directly own. Each of the Reporting Persons specifically disclaims beneficial ownership of the securities reported herein that he or it does not directly own. Item 5(c) is hereby amended and restated to read as follows: Exhibit 1 annexed hereto sets forth all transactions in securities of the Issuer by the Reporting Persons during the past 60 days. Except as otherwise set forth therein, all of such transactions were effected in the open market. Item 6 is amended to add the following: As previously disclosed, Engaged Capital Flagship Master sold short certain exchange listed American-style call options (the "Short Call Options") referencing an aggregate of 200,000 Shares, which had an exercise price of $11.00 per Share and expiration date of May 16, 2025. Prior to the expiration date, Engaged Capital Flagship Master purchased to cover the Short Call Options and, accordingly, Engaged Capital Flagship Master no longer has any exposure to the Short Call Options. Item 7 is hereby amended to add the following exhibit: 1 - Transactions in Securities. Engaged Capital Flagship Master Fund, LP /s/ Glenn W. Welling 09/11/2025 Engaged Capital Co-Invest XVII, LP /s/ Glenn W. Welling 09/11/2025 Engaged Capital LLC /s/ Glenn W. Welling 09/11/2025 Engaged Capital Holdings, LLC /s/ Glenn W. Welling 09/11/2025 Welling Glenn W. /s/ Glenn W. Welling 09/11/2025