2010-11: Eric Cornel played in four minor midget AAA games for the Upper Canada Cyclones and had 61 points in 30 games for the club's bantam AAA team. He scored 1 goal with 3 assists in four midget games.
2011-12: Cornel appeared in four junior A games with the Kemptville 73's in Ontario and was a team captain for the Upper Canada Cyclones' midget minor AAA team as a 15-year-old. He scored 1 goal with 3 assists in CCHL play with Kemptville. Cornel scored 18 goals with 32 assists and had 14 penalty minutes in 25 regular season games for the Cyclones and had 5 assists with 4 penalty minutes in five playoff games. Cornel was an assistant captain for Canada's U16 team at the 2012 Youth Olympic Games; scoring 4 goals with 5 assists and finishing +11 in six games. He was the third player selected when he was taken by Peterborough in the first round of the 2012 OHL Priority Selection.
2012-13: Cornel appeared in 63 of 68 games for Peterborough in his first OHL season and played for Canada Ontario in the 2013 U17 World Hockey Challenge. He scored 4 goals with 12 assists and was -2 with 13 penalty minutes playing for the Petes — who missed the playoffs after finishing with the league's third-worst record. Cornel had 3 assists in five games for Canada Ontario at the WHC.
2013-14: Cornel moved into a prominent scoring role for the much-improved Petes in his second OHL season. Cornel was selected to play for Team Orr in the 2014 CHL/NHL Top Prospects Game.