Upon graduating from the U.S. Air Force Academy in 1966, Grabe went to Darmstadt, West Germany, as a Fulbright Scholar. He returned to the United States in 1967 to complete pilot training at Randolph Air Force Base, Texas. He subsequently flew F-100 aircraft with the 27th Tactical Fighter Wing at Cannon Air Force Base, New Mexico, and in 1969 was assigned as an F-100 pilot with the 3d Tactical Fighter Wing at Bien Hoa Air Base in the Republic of Vietnam, where he flew 200 combat missions.