Following college, Montgomery was signed by the St. Louis Blues. For the 1993–94 season he skated in 67 contests and scored 20 points, both NHL career highs. Following the season the highly touted Montgomery was traded to the Montreal Canadiens for Guy Carbonneau. For the 1994–95 season however things did not work out and after just 5 games Montgomery was released by the Canadiens. Later in the year he was signed by the Philadelphia Flyers and skated in 8 regular season contests and 7 playoff contests with the Flyers. Montgomery is credited with nicknaming the dominant line of John LeClair, Eric Lindros, and Mikael Renberg the "Legion of Doom". The 1995–96 season saw Montgomery play only 5 games with the Flyers but he had a career year with the Flyers minor league affiliate Hershey Bears of the AHL. He scored 105 points in 78 games and was named to the AHL Second All-Star Team.