Intermittent engine issues saw Randle fall back into the clutches of Brown on lap 9, and two laps later he could no longer defy a straight-line deficit as Brown breezed by down Conrod Straight.
The duo had traded fast times through the first half of the 16-lap race to charge away from the rest of the 21-strong combined Super2/Super3 field.
With Randle ailing, Brown went on to take the flag 8.8598 seconds ahead as focus moved to the battle for third.
Jordan Boys made it a one-three for Image Racing, narrowly holding off Tickford Racing teen Broc Feeney.
The race finished with multiple yellow flags waving, including for Jayden Ojeda whose day went from bad to worse.
Ojeda went backwards off the second row of the grid and then lost more ground while trying to pass Matt Chahda into The Chase.
The 21-year-old rookie recovered before crashing out on the last lap at The Cutting, exactly where he’d had a similar incident in the morning Supercars co-driver session aboard the Garry Rogers Motorsport wildcard.
Behind the lead quartet, Chahda won an energetic battle for fifth, capped by a penultimate lap pass on Angelo Mouzouris.
Chahda had been the big winner off the start-line, making up four places and doing his best to keep challengers at bay from there.
Zak Best was sixth from Mouzouris, Josh Fife, Zane Morse and debutant Matthew McLean.
Jaylyn Robotham bounced back from his Thursday practice crash to win the Super3 class in outright 11th, more than 30 seconds ahead of next-best Jon McCorkindale.
Anderson Motorsport’s Declan Fraser had sat between the pair until a front-right failure pitched him into the gravel trap at McPhillamy Park.
Randle’s series lead over Brown has been slashed to 26 points, with another Super2/Super3 qualifying and race to take place tomorrow.
It’s not yet clear whether this will be the final round of the 2020 Dunlop Super2 Series.