This study examines the contextual factors of the external business environment, organization, information systems, and enterprise system software as they affect integration of enterprise resource planning (ERP) systems after a merger or acquisition in the oil and gas industry. A multiple case study method using primary and secondary data revealed: ERPs are operational necessities rather than strategic differentiators; best practice adoption is a viable alternative that supports successful integration of cultures and knowledge from two experienced organizations; schedules are extended when best practices from both companies are consolidated into a single instance; consolidation facilitates Sarbanes-Oxley compliance and lowers the cost of ownership; imposing acquirer systems on targets facilitates timely decision-making and shorter schedules.