The 25-year-old scored his hat-trick goals in the first period, in the 17, 32 and 44 minutes respectively, while Moroccan-born Moestafa El Kabir scored the fourth goal in the 82 minutes.
Simon Alexandersson fine finish was the only consolation goal for Oster in the 76th minutes.
The Gunjur-born player was coming from a 10 match layoff due to injury to make his first start for the Gothenburg-based club.
He helped his team end their five match winless run and was voted the Man of the Match.
Bubacarr’s side OIS as they are fondly called sit ninth position in the Superettan table standings with 29 points, while Oster sits fourth position with 45 points after twenty-five matches.