Glentoran recovered from an early setback to secure a much-needed first Premiership win of the season.
Stephen Hughes gave the visitors a 21st-minute lead with a near post header but Curtis Allen lobbed keeper Jonathan Parr for the equaliser.
Allen, back from suspension, set up Fra McCaffrey to score with a tap-in.
In the second half Glens keeper Chris Keeman saved twice from Stephen McCabe and then Stephen McAlorum set up Allen for his second goal near the end.
It was a relief for Glentoran who will be aiming to improve on their poor home record last season.
The east Belfast men dropped 34 points at the Oval last term, picking up just 23 from a possible 57.