2010-11: Riley Stadel played for the Cloverdale Colts bantam team in suburban Vancouver. He was selected by Kelowna in the third round (51st overall) in the 2014 WHL Bantam Draft.
2011-12: Stadel made his WHL debut — skating in two March games for the Kelowna Rockets — and played one game with the BCHL's Pentincton Vees; spending most of the year with the Okanagan Hockey Academy's Midget Prep team. He had 1 assist and was -3 playing for Kelowna and had no points nor penalties in his only BCHL game. Stadel scored 16 goals with 29 assists and had 64 penalty minutes in 50 regular season games for the OHA's midget team and had an assist and 2 penalty minutes in one playoff game.
2012-13: Stadel made the Kelowna Rockets out of camp as a 16-year-old — skating in 49 regular season games in his first WHL season — and played for Canada Pacific in the 2013 U17 World Hockey challenge. He scored 2 goals with 9 assists and was +14 with 21 penalty minutes. The Rockets finished second in the B.C. Division and reached the second round in the playoffs. Stadel had 1 assist and was -4 with 6 penalty minutes in 11 playoff games. He had no points with 8 penalty minutes in five games for the silver medal Canada Pacific squad at the WHC.
2013-14: Stadel skated in 63 of 72 regular season games for Kelowna in his second season. One of three defensemen with 35 points or more on the WHL's top team, he had 10 goals with 25 assists in 63 games and was +12 with 62 penalty minutes. Stadel was ranked 58th amongst North American skaters in Central Scouting's mid-term rankings prior to the 2014 NHL Draft.