He then joined the NFL in 1976 as a line judge on the crew of Tommy Bell before being promoted to the head referee position in just his second year.
He joined the Big Ten as a full-time back judge in 1966, and in 1968, was promoted to referee after taking charge of a 1967 game between Missouri and Northwestern at Evanston, Illinois, a few miles from his residence in Skokie.
He served as the back judge in the "Game of the Century" on November 19, 1966, between top-ranked Notre Dame and second-ranked Michigan State which ended in a 10–10 tie.
Moments after Hayes' tirade, Markbreit ejected Buckeyes linebacker Randy Gradishar for punching Michigan quarterback Tom Slade through his face mask, triggering a 10-minute brawl.
With 10 seconds left in the game, Raiders quarterback Ken Stabler lost the ball, and it rolled forward towards the San Diego goal line.
Markbreit ruled that Stabler fumbled the ball instead of intentionally throwing a forward pass, and the league backed up the call.
In November 1986, Markbreit was the referee at Soldier Field when the Green Bay Packers visited to play the Chicago Bears.
He ejected Packers defensive end Charles Martin after he bodyslammed Jim McMahon shoulder-first into the AstroTurf.
[7] The call was largely credited by the media and NFL executives in helping Markbreit land the assignment as the referee of Super Bowl XXI two months later.