X0306 4 2021-05-04 0 0001698990 Magnolia Oil & Gas Corp MGY 0001374442 Walker John B C/O ENERVEST LTD. 1001 FANNIN STREET, SUITE 800 HOUSTON TX 77002 1 0 1 0 Class A Common Stock 29503847 I See Explanation of Responses Class A Common Stock 2021-05-04 4 A 0 11522 0.00 A 596320 D EnerVest Management GP, L.C. ("EVM GP") is general partner of EnerVest Ltd., which is sole member, with sole control over the actions of, EVFC GP XIV, LLC, the managing general partner of EnerVest Energy Institutional Fund XIV-C, L.P. ("EV XIV-C"). EV XIV-C owns of record 29,503,847 shares of Class A common stock (the "Reported Securities"). Mr. Walker is an indirect owner and the Executive Chairman of EVM GP. Mr. Walker directly (through ownership or position) or indirectly through one or more intermediaries may be deemed for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, to be the indirect beneficial owner of the Reported Securities owned by EV XIV-C. Mr. Walker disclaims beneficial ownership of the Reported Securities held by EV XIV-C except to the extent of his pecuniary interest in EV XIV-C. This report shall not be deemed an admission that he is the beneficial owner of such securities for purposes of Section 16 or for any other purpose. Reflects restricted stock units ("RSUs") granted under the Magnolia Oil & Gas Corporation Long Term Incentive Plan. Each RSU represents a contingent right to receive one share of Class A common stock of Magnolia Oil & Gas Corporation (the "Company"). The RSUs will vest on the earlier of (a) the day preceding the next annual meeting of stockholders of the Company at which directors are elected, or (b) the first anniversary of the grant date, in each case, subject to the director's continued service through the applicable vesting date. /s/ John B. Walker 2021-05-06