The Ontario Sires Stakes program was established in 1974. The objective of the program is to promote breeding of Standardbred horses in Ontario and to provide economic incentives to breeders to improve the quality of the Ontario Sired horse.

The Ontario Sires Stakes program consists of a series of races for two and three-year-old trotters and pacers, held at tracks across Ontario from May to November of each year.

The program is funded by the Ontario horse racing industry through a provincial levy imposed on wagering at the rate of 3% of total wagering. In addition, 0.3% of wagering is dedicated to the program by the Standardbred horse people from the pari-mutuel tax reduction provided to the industry by the Ontario government. The purses are further enhanced by stallion levies, nomination and sustaining payments and starting fees.

The Program consists of two tiers of racing, a Grassroots Series and a Gold Series. In the Grassroots Series there are five legs, a Grassroots Semi-Final and Grassroots Championship race for each category of age, sex and gait. The Gold Series consists of five legs, followed by a Super Final at the end of the season for each category of age, sex and gait.

In 2020, Ontario Racing added the Prospect Series to the Standardbred Improvement Program and in 2022 it will consist of eight racing opportunities for each age, sex and gait category, contested in five legs.

The foundation of the Ontario Sires Stakes program are the stallions registered with the program. To be eligible to the program the stallion must be owned or leased by an Ontario resident, and stand in the Province for his entire breeding season. Dual Hemisphere stallions must remain in the province of Ontario for 170 consecutive days. Only foals resulting from a mating between a mare in the Northern Hemisphere and a stallion registered for the OSS program are eligible for nomination to the Ontario Sires Stakes.