After leaving the Air Force, Grantham became a citizen airman in the U.S. Air Force Reserves and Air National Guard, where he continued to serve his country as a F-16 Command Pilot. He retired as a Lieutenant Colonel in 2013 with over two hundred combat hours and 2,200 total hours in the F-16. Returning to Augusta in 2017, he currently serves as President & CEO of Eden Innovations LLC. He is a member of the Exchange Club of Augusta and is the founder and Chairman of Paceline Ride, LLC, a non-profit raising money for the Georgia Cancer Center. He and his two sons, Chase and Clay, live in Augusta.

Mr. Grantham was appointed to the GSFC Board of Commissioners November 5, 2020. He was reappointed on January 5, 2021; his term expires January 1, 2027.