In 1975, Dattilio was the first territorial exemption of the Montreal Alouettes, but after a time on the injury list he was released in September[4] and then the next month he signed with the Toronto Argonauts.
The next season, he was released by the Argonauts, rejoined the Alouettes, and served as the third-string quarterback behind Sonny Wade and Joe Barnes.
In March, 1984, Dattilio was traded back to Montreal (by then re-named the Concordes) where he served as a back-up or a third-string quarterback for two more seasons.
Among Canadian quarterbacks Dattilio is second all-time in statistics with 9952 passing yards on 697 completions from 1271 attempts with 53 touchdowns and 79 interceptions.
[6] He is a business person in Calgary, and was inducted into Northern Colorado Athletic Hall of Fame in 2004[7] and had the Gerry Dattilio Sportsfield named after him in Laval, Quebec, in honour of his great Chomedy High School playing days.