It is part of League1 Canada, the national third tier with regional division, along with three other provincial leagues.

The league champion qualifies for the Canadian Championship, Canada's domestic cup tournament.

[6] On April 8, 2014, the OSA revealed its plans for the inaugural season of League1 which would begin during the final weekend in May 2014.

The season featured 10 teams, chosen through a standards-based application process, which were: ANB Futbol, Durham Power FC, Internacional de Toronto, Kingston Cataraqui Clippers, Master's FA, Sigma FC, Toronto FC Academy, Vaughan Azzurri, Windsor Stars and Woodbridge Strikers.

[8] Dylan Sacramento of Toronto FC Academy scored the first ever goal in the league with a 10th-minute strike against Vaughan Azzurri.

Toronto FC Academy were crowned the inaugural league champions on October 4, 2014, after defeating the Cataraqui Clippers 3–1 to secure the top place in the regular season standings.

According to L1O commissioner Dino Rossi, L1O would serve as "CPL's official development league.

[25] Existing teams were assigned to one of the top-two tiers based on the number of points they earned in the previous two seasons.

Under the reorganization, teams have the ability to move up and down between tiers through a process of promotion and relegation.

[29] In 2016 and 2017, the league champion was determined by a single match playoff between the winners of the east and west divisions.

Promotion and relegation results in the Championship team that is crowned champions will automatically be promoted to the Premier, while the team at the bottom of the Premier standings will be automatically relegated to the Championship.

[34] It runs concurrently with the regular season, with cup games usually taking place mid-week.

[note 1] Following the last minute departure of ProStars FC, the league has only 11 teams participating in the 2025 season.

[39] Some of these regulations include: League1 Ontario is an open-age league however there are several rules designed to give playing opportunities to young players.