X0508 4 2026-02-14 0001587732 ONE Gas, Inc. OGS 0001951536 Brumfield Brian F. 15 E. 5TH STREET TULSA OK 74103 false true false false See Remarks false Common stock, par value $0.01 2026-02-16 4 M false 1283.757 86.04 A 3308.844 D Common stock, par value $0.01 2026-02-16 4 F false 438.398 86.04 D 2870.446 D Common stock, par value $0.01 2026-02-14 4 M false 562.680 86.04 A 3433.126 D Common stock, par value $0.01 2026-02-14 4 F false 186.914 86.04 D 3246.212 D Common stock, par value $0.01 1434 I by 401(k) Plan Performance Units 2023 2026-02-16 4 M false 1513 86.04 D Common stock, par value $0.01 1513 0 D Restricted Units 2023 2026-02-14 4 M false 504 86.04 D Common stock, par value $0.01 504 0 D Performance Units 2026 2026-02-16 4 A false 959 86.04 A Common stock, par value $0.01 959 959 D Restricted Units 2026 2026-02-16 4 A false 959 86.04 A Common stock, par value $0.01 959 959 D Performance units awarded under the Issuer's Amended and Restated Equity Compensation Plan (2018). The award, including dividend equivalents, vested on February 14, 2026, in an amount equal to 76% of the performance units awarded based upon Issuer's total shareholder return compared to the total shareholder return of a selected peer group, was certified by the Executive Compensation Committee of the Board of Directors on February 16, 2026, and issued pursuant to the terms of the grant agreement. Restricted units awarded under Issuer's Amended and Restated Equity Compensation Plan (2018). During the 3-year vesting period, the award was credited with dividend equivalents that were paid out in shares of common stock at the time the underlying units vested and were issued. The shares were issued pursuant to the terms of the grant agreement. Performance units awarded under the Issuer's Amended and Restated Equity Compensation Plan (2018). The award will vest on February 17, 2029, for a percentage (0% to 200%) of the performance units awarded based upon the Issuer's total shareholder return compared to total stockholder return of a selected peer group over the performance period from January 1, 2026, through December 31, 2029, in accordance with the terms of the Performance Unit Award Agreement. Restricted units awarded under the Issuer's Amended and Restated Equity Compensation Plan (2018). The award vests on February 17, 2029, in accordance with the terms of the Restricted Unit Award Agreement. Vice President, Chief Accounting Officer and Controller /s/ Brian K. Shore, Attorney-in-Fact for Brian F. Brumfield 2026-02-19