In 1946, Allen joined the Springfield Indians of the American Hockey League, for whom he played the next five seasons.

In February 1954, Warriors owner Eddie Shore tried to assign Allen to the Springfield Indians of the Quebec Hockey League, but he (along with several other players) balked and he was suspended.

He spent most of the 1954–55 season in the Western Hockey League with the Edmonton Flyers—Detroit's farm team, whose roster included future Hockey Hall of Fame inductees Johnny Bucyk, Norm Ullman, Glenn Hall, Al Arbour, and player-coach Bud Poile.

From 1956 to 1965, Allen was a head coach in the Western Hockey League with the Seattle Americans/Seattle Totems, with only one losing season in eight years.

They fell to third place in their division in the 1968–69 NHL season, and Allen then became the Flyers' general manager while serving in the same capacity with the Quebec Aces at the same time.

There, he would help construct the famed "Broad Street Bullies" that led the Flyers to consecutive Stanley Cups in 1974 and 1975.