X0306 4 2019-03-01 0 0001486159 Oasis Petroleum Inc. OAS 0001494078 Reid Taylor L 1001 FANNIN ST, STE 1500 HOUSTON TX 77002 1 1 0 0 President and COO Common Stock 2019-03-01 4 A 0 55886 0.00 A 1451989 D Common Stock 2019-03-01 4 F 0 21991 5.57 D 1429998 D Common Stock 2019-03-01 4 A 0 21040 0.00 A 1451038 D Common Stock 2019-03-01 4 F 0 8279 5.57 D 1442759 D Common Stock 525000 I By West Bay Partners, Ltd. Represents shares issuable to the reporting person in settlement of a grant of performance share units made on January 20, 2016. On March 1, 2019, these shares were determined to have been earned, and they vested on such date. Represents shares issuable to the reporting person in settlement of a grant of performance share units made on January 12, 2017. On March 1, 2019, these shares were determined to have been earned, and they vested on such date. A limited partnership formed for family investment purposes. The sole general partner of West Bay, a Texas limited liability company, is controlled by the reporting person and his wife, and the limited partners of West Bay consist of the reporting person, his immediate family members and trusts formed for their benefit. /s/ Nickolas J. Lorentzatos, as attorney-in-fact 2019-03-04