Danny Purkis struck with two minutes to go to send Glentoran up to fourth place in the table as they edged out Ballymena United at The Oval.
Just when it looked like they would have to make do with a point Shay McCartan unlocked the resolute Sky Blues defence, picking out Purkis, who coolly finished past Jordan Williamson for only their second win in six games.
The hosts started on the front foot with Conor McMenamin curling an effort narrowly wide of the far post with only seven minutes on the clock.
