Coleraine lost ground in the Premiership title race after this defeat by Glenavon at the Showgrounds.
Ciaran Martyn lifted the ball over keeper Michael Doherty and into the net to give Glenavon a 20th minute lead.
Curtis Allen hit a post for the hosts while Glenavon's Ciaran Doherty was also denied by the woodwork.
Andy McGrory rifled home 10 minutes to make it 2-0 from time and Coleraine defender Howard Beverland was dismissed soon after for two yellow cards.
The Lurgan Blues were first to go close when Michael Doherty turned away Michael Doherty's strike.
Ruairi Harkin blasted over the rebound after Allen's shot found a post in what was a lacklustre display from the Bannsiders.
Michael Doherty produced a good save to keep out Martyn's close-range effort on the rebound after Ciaran Doherty's header hit the crossbar.
McGrory hit the net after a Guy Bates shot was blocked and substitute Andy Mitchell wasted a late chance to add a third for the visitors.
Coleraine remain fourth but they they now trail leaders Cliftonville by nine points while Glenavon move up a place to ninth.