UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Quarterly Period Ended March 31, 2023 ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission File Number 0-18082 GREAT SOUTHERN BANCORP, INC. (Exact name of registrant as specified in its charter) Maryland 43-1524856 (State or other jurisdiction of incorporation (I.R.S. Employer Ident ...