Bottom-placed Glenavon got their first Premiership win of the season despite playing with just 10 men for the entire second half.
Former Newry front man Andy Graham got the goal in the seventh minute after a dummy by Diarmiud O'Carroll left him free to shoot past Michael Doherty.
Coleraine's Johnny Black hit the bar with a swerving free-kick while Curtis Allen had three headers saved.
Glenavon's Ryan Harpur was sent-off for two yellow cards on 42 minutes.
The second caution was for a foul on Black.
Glenavon had Mark Haughey stretchered off with a serious-looking injury to his right leg in the 32nd minute.
Marty Quinn's men are still bottom of the table but are now just two points behind Carrick Rangers.