2010-11: Michael Dal Colle played for the Vaughan Kings minor midget AAA team in Ontario as a 14-year-old and was a team captain for the club's bantam AAA team.
2011-12: Dal Colle appeared in five junior A games with the St. Michael's Buzzers of the Ontario Junior Hockey League, including one playoff contest, and was the leading scorer for the Vaughan Kings minor midget AAA team. He had no points with 4 penalty minutes skating for the Buzzers. Dal Colle drew the attention of both NCAA college coaches and OHL scouts — scoring 44 goals with 34 assists in 42 midget games for Vaughan. The Kings participated in the OHL Cup and in five games Dal Colle scored 4 goals with 7 assists. He was the seventh player taken in the 2012 OHL Priority Draft when he was selected by the Oshawa Generals in the first round.
2012-13: Dal Colle chose the junior route over college hockey — and was the fifth-leading scorer for a powerful Oshawa squad that featured NHL prospects Boone Jenner (Columbus), Scott Laughton (Philadelphia) and Tyler Biggs (Toronto). He scored 15 goals with 33 assists in 63 regular season games and was +19 with 18 penalty minutes. The Generals finished second in the East Division and advanced to the second round. Dal Colle scored 2 goals with 3 assists and was +3 with 6 penalty minutes in nine OHL playoff games. Skating for Canada Ontario in the 2013 U17 World Hockey Challenge he scored 2 goals with 4 assists in five games.
2013-14: Dal Colle played for the gold medal-winning Team Canada U18 team in the 2013 Ivan Hlinka Memorial team in August before returning to Oshawa for his second OHL season. In five games at the Ivan Hlinka tournament he scored 2 goals with 2 assists anew as -1 with 4 penalty minutes.