Toronto Argonauts

McEwen was drafted by the Toronto Argonauts third overall in the first round of the 2015 CFL Draft after being ranked as the tenth best overall player available by the CFL Central Scouting Bureau.^[1] Shortly after the draft, he attended mini-camp with the National Football League's New York Giants, but was not signed by the team and he returned to the University of Calgary for his final year.^[2][3]

On May 13, 2016, it was announced that McEwen had agreed to a three-year contract with the Argonauts.^[4] He appeared in 16 games during the 2016 season, starting in 11, en route to being named the Argonauts nominee for Most Outstanding Rookie. On March 9, 2017, it was announced that McEwen had signed an extension through the 2019 season.^[5] At the end of that year, he was named a CFL All-Star at centre.

In 2019, he was the Toronto Argonauts' Most Outstanding Offensive Lineman.^[6] Over four seasons, he had played in all 72 regular season games as well as two post-season games, including a win in 105th Grey Cup game. As a pending free agent in 2020, he was released during the free agency negotiation window on February 7, 2020.^[7]

Calgary Stampeders

On February 8, 2020, it was announced that McEwen had signed a two-year contract with his hometown Calgary Stampeders.^[8]