Lisa MacLeod's motion to get the auditor general to review the Ontario Lottery and Gaming Corporation's future plans passed at Queen's Park on Thursday afternoon.
The cash-strapped government has proposed pulling OLG slot machines from racetracks in an effort to balance the books.
More than $300 million a year in slot-machine revenue was going toward the prize purses of horse races.
Breeders, racetracks and owners argue those millions have a spinoff effect that supports their entire industry and puts more than $1 billion into the economy.
They rallied at Queen's Park Thursday to protest the province's decision to shut down its racetrack slots programs.
MacLeod said moving slot machines to proposed urban casinos could be the wrong move.
"The numbers being put forth by the government are being challenged by an industry and our agricultural communities right across the province," said MacLeod. "I'm proud to stand with the NDP and Progressive Conservative caucus in supporting these people in the gallery and supporting those 60,000 jobs."
A government-commissioned report last week said the governing Liberals were right to end the slots-at-racetracks program.
But it also suggested an alternative needs to be put in place so the horse racing industry doesn't collapse.