Goals by substitutes Andrew Waterworth and Peter Steele proved enough to give Glentoran the points against Lisburn Distillery.
Waterworth, who came on a half-time for Matty Burrows, scored with his first touch in the 48th minute.
The Glens striker outpaced Andy Hunter before beating Billy Brennan at the second attempt.
Peter Steele made it 2-0 in the 90th minute before Glenn Ferguson scored for Distillery in stoppage-time.
Ferguson struck a half-volley from eight yards past keeper Elliott Morris but it was not enough to deny Glentoran the win.
Before the match, Glens players Paul Leeman and Grant Gardiner were injured in the warm-up.
That meant Jimmy Callacher started the game and the home side had just four substitutes.
Mark Patton put a 10th-minute chance over for Distillery while Glentoran's Michael Doran headed on to the roof of Brennan's net.
Johnny Black tested Brennan with a free-kick and Daryl Fordyce put a right-foot efffort narrowly wide.