Oncor COO James Greer to Retire; Company Appoints New CFO and COO for 2026
Leadership transition brings long-time Oncor veterans Don Clevenger and Ellen Buck into top executive roles.
October 30, 2025
Leadership Reshuffle at Oncor as COO Plans Retirement
Oncor is preparing for a change in leadership. James A. Greer, who has served as Executive Vice President and Chief Operating Officer, will step down from his role on December 31, 2025. His retirement sets the stage for a new phase in the company’s executive lineup.
The next day, January 1, 2026, two key promotions go into effect. Don J. Clevenger will become Executive Vice President and Chief Financial Officer. Ellen E. Buck will take on the role of Senior Vice President and Chief Operating Officer. Both are long-time Oncor leaders who bring deep operational and financial experience into their new roles.
Clevenger, currently serving as SVP and CFO, has been in that role since 2018. With this change, he steps into a broader executive position while continuing to lead the company’s financial direction.
Buck, who currently leads Business and Operations Services, has been with Oncor since 2005. Over that time, she’s managed teams across asset planning, transmission development, engineering support, and supply chain. Before her time at Oncor, she worked as a transmission engineer at Georgia Transmission Corporation and is a licensed Professional Engineer in Texas.
Her new role as COO makes her responsible for overseeing the company’s operations—from transmission to innovation—on a company-wide scale.
This transition brings experienced leadership into sharper focus. Oncor is making sure its operations stay aligned, its strategy stays grounded, and its leadership continues to reflect the technical strength of the organization. Greer’s departure opens the door, but it’s the continuity in these appointments that will shape what’s next.
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