Darren Boyce struck with nine minutes left to give the Glens victory over the Carling Premiership leaders.
The Blues had the wind on their backs in the first half and Michael Gault and Daryl Fordyce went close before Robert Garrett wasted a good chance.
Ciaran Martyn fired wide for the hosts while Elliott Morris pushed Peter Thompson's header onto the crossbar.
The Glens rarely threatened but they won it when Boyce headed into the top corner from a Stephen Carson cross.
Jamie Mulgrew's corners provided the only threat early in the game with Gault heading over from eight yards before Fordyce's glancing header was blocked.
The windy conditions contributed to an error-strewn first half with few chances although Garrett should have done better when he volleyed tamely into the arms of Morris just before the break.
Glentoran improved with the wind advantage in the second half and Martyn's low shot was just off-target soon after the restart.
However, the Blues still possessed the greater threat with Thompson denied by the woodwork before Fordyce hit the side-netting.
The goal came from a rare moment of quality between two former Coleraine team-mates.
Carson's pinpoint cross to the far post found Boyce and his close-range header arrowed into the net.
Linfield pushed for an equaliser and Garrett's long-range shot was punched out by Morris in the dying seconds.
The Glens stay fifth in the table while Linfield's lead at the top is cut to two points after Portadown's win at Glenavon.
Meanwhile, Glentoran have completed the signings of former Derry City defender Stewart Greacen and winger Eamonn Murray from Ballymena United on 18-month deals.