He played in Major League Baseball for the Baltimore Orioles, Atlanta Braves, Cleveland Indians, and Minnesota Twins from 1972 to 1978.

Harrison amassed a 13–28 record in Houston's farm system and pitched just two innings for the Oklahoma City 89ers in 1969 when he was dealt to the Seattle Pilots with Dooley Womack for Jim Bouton.

Harrison pitched for the franchise's (now known as the Milwaukee Brewers) triple A affiliate, the Portland Beavers in 1970, and went 6–11 with a 5.57 earned run average.

After just one season in Baltimore, Harrison was traded along with Davey Johnson, Pat Dobson and Johnny Oates to the Atlanta Braves for Earl Williams and Taylor Duncan on the last day of the Winter Meetings on December 1, 1972.

Harrison was 20–23 with a 4.45 ERA in his career for Atlanta when he was dealt to the Cleveland Indians during the 1975 season for pitcher Blue Moon Odom.