Sixth-placed Glentoran moved four points clear of Portadown in the league table thanks to Richard Clarke's 58th-minute winning goal at Shamrock Park.
Sean Mackle missed a 22nd-minute penalty after Gary Twigg had been fouled by Jay Magee inside the area.
Clarke's strike hit the inside of the post before nestling in the bottom corner of the net.
Kevin Braniff went close on three occasions while Magee was sent-off for a second bookable offence after 75.
After a disappointing first half, the match fired into life when Kevin Braniff missed two early chances at the start of the second period.
Clarke gave the Glens the lead, before Elliott Morris made a brilliant save from a Braniff free-kick and the forward was denied again when David Howland headed his effort off the line.
Magee was sent-off for two yellow cards after fouling Twigg as he bore down on goal.
Morris produced another good save from Braniff while, at the other end, Andy Waterworth saw his attempt blocked by David Miskelly.