Bennett smashed an angled drive into the top corner from 20 yards as the Seagulls stretched their unbeaten away run to eight games.
Oldham should have taken the lead after just two minutes but Pawel Abbott headed off target from six yards after fine work by Lewis Guy.
Brighton slowly took charge and Bennett rammed home his sixth goal of the season in the 40th minute, cutting in from the left to leave Oldham keeper Darryl Flahavan helpless.
Brighton's Peter Brezovan preserved the lead with an agile double save from Abbott and Chris Taylor.
The visitors went two up in the 57th minute after suicidal Oldham defending led to a Seb Carole cross which was sliced into his own net by Jon Worthington.
Under-fire Latics manager Dave Penney saw his team handed a late lifeline when they were awarded a penalty for handball against Tom Elphick but Brezovan saved Abbott's spot-kick and the rebound was fired against the underside of the crossbar by Tom Eaves.