Mr. McCollum joined the Marathon Oil board of directors in 2022.

He formerly served as the president and chief executive officer of Weatherford International plc from April 2017 to June 2020. Before joining Weatherford, Mr. McCollum served as executive vice president and chief financial officer of Halliburton Company, a position he assumed in 2008 and resumed in July 2016 following an interim role from December 2014 to July 2016 as executive vice president and chief integration officer. From 1995 to 2003, Mr. McCollum held several senior positions at Tenneco, Inc., including chief financial officer. From 1991 to 1995, he served as an Audit and Advisory Partner in Arthur Andersen's Energy Division, where he began his career.

Mr. McCollum serves on the boards of directors of Westlake Corporation, Seadrill Limited and Baylor College of Medicine. He is also a director at Baylor St. Luke’s Medical Center and Yellowstone Academy.

He holds a bachelor's degree in business administration in accounting from Baylor University and is a Certified Public Accountant in Texas.