That year he earned the first of six trips to the Pro Bowl, before being called into military service.

The Baltimore Colts who acquired his rights before the start of the 1953 season, traded him to the Cleveland Browns in a massive 15-player deal. Even though the Browns knew Mike would not be available for a full year, he was the key man in the trade. Coach Paul Brown always considered it one of his wisest personnel moves.

In his first season in Cleveland, McCormack, a former University of Kansas star and Chicago native, was asked to fill the middle guard position that had been vacated by the retiring Bill Willis on the defensive unit. It was a tall order, considering Willis would himself be elected to the Hall of Fame. McCormack, not surprisingly, was up to the challenge.

He quickly became an important factor on an excellent Cleveland defensive team. Mike enjoyed perhaps his most memorable individual moment on the defensive team when, in the 1954 NFL Championship Game, he stole the ball from Detroit Lions quarterback Bobby Layne to set up one of the early touchdowns in a 56-10 Cleveland rout.

But it was as an offensive tackle that McCormack made his lasting mark in pro football. Mike was the Browns' offensive right tackle for eight years from 1955 through 1962. During that period, the Browns’ forward wall played a major role in assuring a balanced offensive approach and McCormack, equally adept as a blocker on rushing plays and as a quarterback protector, was a stabilizing factor throughout the period.