After one year in the Phillies organization, Harrah was drafted by the Washington Senators in the fall of . After a brief callup in 1969, he advanced to the major league club in ; the next year the franchise relocated and became the Texas Rangers. He was the regular shortstop through , then moved to third base, although he still saw some action at short. He was selected to the American League All-Star team in , , and . He had a career-best 93 RBIs in 1975. On June 25, 1976, Harrah played an entire doubleheader at shortstop without recording a single chance in the field. The following season he and teammate Bump Wills hit back-to-back inside-the-park home runs.