The MSR Camaro driver was untroubled across the 35 laps as he became the second surprise winner of the weekend, following Mark Winterbottom's drought-breaking victory yesterday.
It marked a first win for MSR and second for Le Brocq, who took a maiden victory at Sydney Motorsport Park in 2020 when driving for Tickford Racing.
It also followed a frantic repair job by MSR after Le Brocq's car was damaged in the earlier race today.
"I dunno, I'm a bit lost for words to be honestly," said Le Brocq.
"It's pretty unreal. The guys have done an awesome job, especially the last few hours getting this thing back together, it was pretty beat up after that second race today.
"I feel like it's been a long time coming. The heart rate is still going, it will take a whole to come down. That was a long 35 laps."
Le Brocq converted pole at the start of the race, matching Andre Heimgartner's launch and then having the line through the long first corner.
The pair quickly settled into a rhythm separated by just over a second, while Winterbottom withstood an early challenge from Broc Feeney to hang on to third place.
Having not found a way through, Feeney decided to try an undercut by pitting first of the lead group on lap 16.
Le Brocq, Heimgartner and Winterbottom all covered off the following lap, Feeney jumping Winterbottom in the process, while Will Brown also managed to force his way past the veteran at turn 1.
His move was deemed a little too forceful, though, Brown promptly hit with a five-second penalty.
Out front the second stint was similar to the first, Heimgartner able to shadow Le Brocq but not make any serious play for the lead.
That was the case until the finish, Le Brocq crossing the line 1.3s ahead of Heimgartner.
Feeney ended up a lonely third, 8.5s behind the winner, particularly after the five seconds was applied to Brown, who was fourth across the line.
That dropped the title contender to sixth in the final standings and promoted Shane van Gisbergen to fourth and Cam Waters to fifth.
Winterbottom came home seventh ahead of Will Davison, Chaz Mostert – who charged his way up from 25th on the grid – and Todd Hazelwood.
Series leader Brodie Kostecki had a shocker, meanwhile, finishing the race dead last, more than four laps down on the winner.
His race unravelled on the opening lap when, after starting 11th, he made contact with Anton De Pasquale at the hairpin.
That left him with damaged steering that required a lengthy stint in the garage for the repairs.
As a result what had been a 109-point gap over Brown in the standings was reduced to 59 points, while Feeney is now within 91 points of the Kostecki.
