Since 2001, OSBA has been a mainstay of the senior baseball landscape in Southern Ontario. 

In 2026, 

The Whitby Canadians aim to defend their title and the Milton Orioles will be chief amongst their pursuers after coming within an out of winning the championship last year.

In 2025, six teams attended various levels of the provincial championships and hopefully that number will grow this year.

2026 Eastern Conference
Bowmanville
Clarington
Markham
Port Hope
Whitby

2026 Western Conference
Martingrove
Milton
Mississauga Southwest
Vaughan
York