The Senators selected McCormick, a forward from De Pere, Wisconsin, in the sixth round (No. 171) of the 2011 NHL Draft. McCormick played three seasons at Ohio State, finishing with 88 points (36 goals, 52 assists) in 104 games, and made the Central Collegiate Hockey Association All-Rookie team for the 2011-12 season.
The Senators signed him to a two-year contract on May 28, 2014. He spent most of the next two seasons with Binghamton, Ottawa's affiliate in the American Hockey League, but made his NHL debut against the Arizona Coyotes on Oct. 24, 2015. He got his first NHL assist Dec. 29, 2015, against the Boston Bruins and his first NHL goal on Jan. 7, 2016, in a 3-2 loss to the Florida Panthers.