He played for the New York/San Francisco Giants, Baltimore Orioles, Washington Senators, New York Yankees and Kansas City Royals from 1956 to 1971.

Signed by the Giants as a bonus baby, McCormick went directly to the major leagues and made his debut on September 3, 1956.

After spending seven seasons with the organization, he was traded to the Baltimore Orioles and played two years there before being dealt again, this time to the Washington Senators.

[2] McCormick made his major league debut for the Giants on September 3, 1956, at the age of 17,[1] relieving Rubén Gómez in the ninth inning and retiring all three batters he faced in a 5–1 loss against the Philadelphia Phillies.

[6] He made two starts later in the season, and finished with a 0–1 win–loss record and a 9.45 earned run average (ERA) in 6+2⁄3 innings pitched.

[10] He was acquired along with Stu Miller and John Orsino by the Orioles from the Giants for Jack Fisher, Billy Hoeft and Jimmie Coker on December 15, 1962.

[11] At the end of the 1966 season, McCormick returned to the Giants in a trade that brought Cap Peterson and Bob Priddy to the Senators.

[citation needed] After three years in that field, he switched to office machines and copiers, working for Ricoh and then Danka, before retiring in 2002.

[5] McCormick's Cy Young Award plaque was damaged in the 1989 Loma Prieta earthquake after it fell off the wall of his Cupertino condominium.