Mississauga

The OHL originated in Mississauga with the Mississauga IceDogs. The IceDogs played in Mississauga from 1998 to 2007 being purchased by Ottawa Senators owner Eugene Melnyk in 2006. Following the 2006–2007 season, Melnyk sold the Icedogs who moved to St Catherines to become the Niagara IceDogs. At the same time Melynk moved the Toronto St. Michael's Majors to Mississauga to become the Mississauga St. Michael's Majors. The Majors played in Mississauga from 2007 to 2012, also hosting the 2011 Memorial Cup. Following the 2012 season Melnyk sold the Majors franchise to Elliott Kerr of Mississauga's Landmark Sport Group. As a part of the sale, the Majors identity was returned to St. Michael's College, allowing the team to move forward under the fan-selected "Steelheads" moniker.

The Steelheads struggled in their first season in 2012–13 finishing last in the OHL Central division and eighth overall in the Eastern Conference before losing to the Belleville Bulls in six games in the first round. Before the 2013–14 season the Steelheads drafted 15-year-old Sean Day. Day had applied for and been granted Exceptional Player Status to be able to be drafted into the OHL at 15 years old. In the 2013–14 season the Steelheads again finished last in the Central division and eighth in the Eastern Conference, this time being swept by the number one ranked Oshawa Generals in four games in the first round of the 2014 OHL playoffs. In 2014–15, the Steelheads finished in fourth in the Central division ahead of the Sudbury Wolves but missed the 2015 OHL playoffs finishing five points back. In 2015–16, thanks to strong performances by a trio of top 2016 NHL Entry Draft picks (Alexander Nylander, Michael McLeod, Nathan Bastian) the Steelheads finished above .500 for the first time and ended the season in seventh in the Eastern Conference standings,(fourth in their division). Again though the Steelheads would fall in the first round losing to the Barrie Colts in seven games.^[]

The 2016–17 season was backed by continued strong performances by Bastian and McLeod as well as a breakout 44-goal season from 2017 first round draft Pick Owen Tippett, the Steelheads won their first Central division title. Entering the 2017 OHL playoffs as the second seed in the Eastern Conference, the Steelheads defeated the Ottawa 67's in six games in the first round before defeating the Oshawa Generals in five games in the second round. In the Eastern Conference Finals the Steelheads swept the Peterborough Petes in four games to win their first Bobby Orr Trophy in franchise history. The Steelheads would fall in the J. Ross Robertson Cup Finals in five games to the Erie Otters.^[]

In 2017–18, Mississauga returned to the bottom of the Eastern Conference ending the season in seventh place (fourth in the Central division). The Barrie Colts once again defeated the Steelheads in the first round of the playoffs, this time in six games. In 2018–19, Mississauga was the best team of a weak bottom half of the OHL Eastern Conference finishing in fifth place but 20 points back of Sudbury in fourth. In the playoffs the Wolves easily swept Mississauga in four games. The 2019–20 OHL season was cancelled before completion of the regular season, the J. Ross Robertson Cup or the 2020 Memorial Cup in Kelowna. At the time of cancellation the Steelheads sat in sixth place in the OHL Eastern Conference with a record of 27–29–4–1, but 17 points up on ninth place, which would have guaranteed the Steelheads a seventh playoff appearance in eight seasons.^[]

The Steelheads have proposed to relocate to Brampton for at least the 2024-25 season, pending approval from the OHL.