The dynamic 22-year-old attempted to reach his maiden BBL century with a six down the ground, but Matt Renshaw took an impressive catch near the rope with the Renegades still requiring 17 to win.
But O’Neill (16 not out) finished the job as the Renegades chased down the Heat’s 4-196 with 12 balls to spare.
Fraser-McGurk, who missed out on selection for Australia’s Champions Trophy squad last week, entered the match having scored just 93 runs from his first nine BBL games this season.
But he destroyed a star-studded Heat bowling attack containing internationals Spencer Johnson, Xavier Bartlett, Mitchell Swepson and Michael Neser.
It was the dynamic 22-year-old’s best BBL score and his third fifty in 45 matches in the competition.