Stephen left Tulloch Lodge after 17 years to pursue a training career in his own right. He took the opportunity to be the private trainer for Paul Fudge's Waratah Thoroughbreds.

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The first winner came within five months of training with Riot Act saluting at Nowra.

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To prove that this was no fluke, Riot Act then went on to win again two weeks later at Goulburn. This kicked off a string of winners for Stephen, who enjoyed ten more winners for Waratah Thoroughbreds in a short space of time.

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Another highlight came with his first city winner, Prince of Arragon, who won at Warwick Farm. Some other memorable winners in the Waratah silks are Lost Impact, Stellar Performer and Himiko. 

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In May 2021, Stephen moved to Hawkesbury Race Club to set up his own business. But, again, it didn't take long for the wins to start coming. Martini Crusader was Stephen O'Halloran Racing's first winner when victorious at Newcastle. Wins by Superago and Oceans One soon followed.