Bargwanna (GRM Peugeot) made steady progress in the early part of the 15-lapper, moving into third after front-row starter Luke King (MPC Audi) spun out of the lead on the opening lap.
The ex-Supercars regular then marched past Tony D’Alberto (Wall Honda) to grab second place on the second lap, before settling in behind Race 1 and 2 winner Chaz Mostert (MPC Audi).
The gap hung at just over a second for a number of laps, before Mostert’s tyre condition started to drop off.
Sensing a shot at the win Bargwanna had a near miss on Lap 9 when he overcooked it into Turn 1 and took a trip across the grass.
He was able to recover without losing a spot and swiftly made the time lost to Mostert back up. Then, three laps from home, Mostert’s Audi blew its right-front tyre, handing Bargwanna a lead he held until the end.
The win comes almost a decade after he stepped away from full-time racing in Supercars, and follows a frantic rebuild of his Peugeot thanks to his frightening brake failure at Symmons Plains several weeks back.
“It was going really well and I was catching Chaz, then I got behind him and got massive aero wash into Turn 1,” said Bargwanna of his mid-race moment. “That got my attention!”
“You know you’re having a good day when you’re chasing Chaz to the finish line.
“To come back to GRM and with [son] Ben [Bargwanna] as my teammate, it’s pretty emotional stuff. I’ve been doing this for a long time, and to be able to come back and get [a first place trophy] is pretty special.
“The guys at GRM worked hard to fix this old girl after Tassie and it was a jet for that last race. We were out of the window in qualifying but we worked out way to it.”
D’Alberto moved his way up to second to mark a huge turnaround from a poor weekend for the Hondas in Tasmania, while Nathan Morcom rounded out the podium in his HMO Hyundai.
John Martin (Wall Honda) and Michael Clemente (MCM Honda) were next, followed by Ben Bargwanna (GRM Peugeot), Dylan O’Keeffe (GRM Renault), Jay Hanson (ASM Alfa), Josh Buchan (HMO Hyundai) and Aaron Cameron (GRM Peugeot).
Mostert finished down in 18th thanks to his unscheduled stop, but held on to the series lead.
He had good company at the back end of the field too, with Bathurst 1000 co-driver Lee Holdsworth (ASM Alfa) struggling with more mechanical issues, and another fresh Supercars convert Michael Caruso (GRM Alfa) in 17th after starting from pitlane due to a pre-race clutch issue.