The striker, who is on loan from Cheltenham, scored twice and created the other as Russell Slade's strugglers chalked up their third win in four games.
Owusu has now bagged four goals in as many matches and the Seagulls are one point adrift of safety with a game in hand on Carlisle and Crewe, the teams they are trying to catch.
Owusu wasted an early chance when he side-footed straight at Oldham's veteran keeper Mark Crossley.
He made amends in the 26th minute after turning past Sean Gregan and delivering an inviting cross to the far post for the pint-sized Dean Cox to score with a free header.
Owusu doubled Brighton's advantage in the 37th minute, although it had a touch of good fortune about it.
His striker partner, Gary Hart, delivered another inviting cross. Owusu mis-directed his diving header but it deflected in off the scrambling Crossley.
Oldham, in mid-Table with nothing to play for, were awful in the first half but a few stern words from Joe Royle saw them re-emerge in much more determined mood.
Daniel Jones and Neal Eardley both tested Brighton keeper Michels Kuipers and Gary Dicker cleared a scrambled effort from Chris Taylor off the line.
The visitors deservedly hauled themselves back into the game as substitute Lewis Alessandra ran through the middle to slot home, but they threw away their chances just two minutes later.
Kuipers' through ball should have been dealt with by Gregan and Reuben Hazell but they got themselves into a muddle, leaving Owusu clear to finish calmly past Crossley.
Brighton's victory was marred in the closing stages by a red card for defender Andrew Whing.
He had already been booked when he needlessly knocked the ball away after conceding a throw-in.