X0306 4 2020-03-18 0 0001587732 ONE Gas, Inc. OGS 0001239209 GIBSON JOHN WILLIAM 15 E. 5TH STREET TULSA OK 74103 1 0 0 0 Common stock, par value $0.01 2020-03-18 4 P 0 1620 71.7975 A 270897 I See footnote Common stock, par value $0.01 2020-03-18 4 P 0 1797 73.4155 A 272694 I See footnote This transaction was executed in multiple trades at prices ranging from $71.78 to $71.80. The price reported above reflects the weighted average purchase price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected. Purchased by the Kristie C. and John W. Gibson Revocable Trust. The reporting person is co-trustee of the Kristie C. and John W. Gibson, Revocable Trust. The reporting person disclaims beneficial ownership of the reported securities except to the extent of his pecuniary interest therein. This transaction was executed in multiple trades at prices ranging from $73.41 to $73.43. The price reported above reflects the weighted average purchase price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected. /s/ Brian K. Shore, Attorney-in-Fact for John W. Gibson 2020-03-19