He made his major league debut with the Royals on August 13, 1975 against the Baltimore Orioles, pitching one inning, striking out one and walking one.

[2] McClure spent most of 1976 with the triple A Omaha Royals, appearing in only eight games and pitching only four innings with the big league club.

In 1982, he was moved to the starting rotation and had a 12–7 mark for the American League champion Brewers, but he returned to the bullpen after incumbent closer Rollie Fingers was unavailable for the postseason.

He signed with the New York Mets shortly afterwards, where he was reunited with his CSM teammate Keith Hernandez, with whom he also played Little League baseball when they were younger.

For the 2006 season, new Royals manager Buddy Bell asked McClure to replace Guy Hansen as their new pitching coach.

[5] In November 2011, the Boston Red Sox confirmed reports that they had hired McClure as a scout, roving minor league pitching instructor, and special assistant for player development.

[8] On November 21, 2013, he was named to manager Ryne Sandberg's staff as the 2014 pitching coach of the Philadelphia Phillies, succeeding Rich Dubee.