A second 4-1 away win in successive weeks propelled Glenavon into second place in the Premiership table.
Kyle Neill converted Eoin Bradley's cross with a fine finish on 45 minutes, then Bradley smashed a left-foot shot past Dwayne Nelson in the 54th minute.
Rhys Marshall took advantage of a Nelson blunder to tap in on 71 and Gary Hamilton curled the ball into the bottom corner with seven minutes left.
Allan Jenkins headed in a cross from the left with a minute remaining.
Ballymena began the game brightly as they sought to improve on a record of just one win in their previous six league outings.
Matthew Tipton just failed to get a touch on an Alan Teggart cross, while Neal Gawley blasted over and Alan Blayney saved from Kyle McVey.
Goals from Neill and Bradley put the Lurgan Blues in control, before full-back Marshall had the simple task of finding the net after Nelson dropped the ball at his feet.
The home goalkeeper had an attempted clearance kick charged down, before spilling the ball and tripping over himself.
Some good interplay between Hamilton and Andy McGrory ended with the player-manager finding the net.
Ballymena's unbeaten home record comes to an end and the Sky Blues drop to eight place in the league standings.