Ian Parkhill’s strike on 53 minutes gave Coleraine their first home win over Glentoran since 2012.
The Ballymoney man finished well from close range after some great play from Darren McCauley.
The win moves the Bannsiders on level points with the Glens, who struggled to get going on the day.
Oran Kearney sprung a surprise at the start pushing captain Howard Beverland into a defensive midfield role and handing a start to teenager Lyndon Kane at right back.
Both though produced impressive performances on the day.
Ruairi Harkin was first to try his luck on seven minutes, but his low drive never troubled Elliott Morris.
The visitors did have the ball in the box on 16 minutes, but Curtis Allen’s strike was chalked off for offside.
Coleraine went straight up the pitch and a flowing move was almost finished off by Mark Miskimmin, but his smart turn and volley ended up on the wrong side of the post.
Eddie Patterson’s side should have broken the deadlock on 30 minutes after a calamity of errors in the Coleraine defence.
Stephen Douglas’ attempted clearance cannoned off Marcus Kane’s head and inadvertently teed up Allen, but he somehow fired wide of the target with the goal at his mercy.
Steven Gordon did better from distance six minutes later, his dipping volley had Michael Doherty at full stretch as he tipped it around the post.
Coleraine made a bright start to the second half with Ian Parkhill and Ruairi Harkin both trying their luck from distance.
The deadlock was finally broken on 53 minutes as McCauley eased past Henderson before picking out the unmarked Parkhill, who produced a smart finish into the bottom corner.
Glentoran came close to an equaliser on 60 minutes as Jay Magee flicked on Johnny Addis’ long throw, but Doherty produced an excellent save to flick it over the bar.
Shane McGinty was denied by a good save from Elliott Morris on 75 minutes before Allen saw his free kick clip the bar in the closing stages.
The Glens piled on the pressure in the dying minutes but they just couldn’t find a goal.
Coleraine: Doherty, Kane, Mullan, Ogilby Douglas, Harkin, McCafferty, Parkhill, Beverland, Parkhill, McCauley (McNeill 63), Miskimmin (McGinty 72).
Sub: McIlmoyle, Hegarty, Watt.
Bookings: Miskimmin, Ogilby.
Goal: Parkhill (53)
Glentoran: Morris, Garrett (Magge 25), Kane (O’Hanlon 72), Scullion (McKee 63), Allen, Stewart, Henderson, McAlorum, Addis, Gordon, McCullough.
Subs: Hogg, Holland.
Referee: S Wallace (Londonderry).