Glenavon came back from 1-0 and 3-1 down but ultimately paid the price for some defensive lapses when Sky Blues substitute Shane McGinty fired in a fourth goal for the hosts just moments after he had replaced Jonny McMurray.
McMurray had teed up Andy McGrory for the opening goal in the 8th minute after an error by Caolan Marron but Seamus Sharkey equalised ten minutes later. The United striker got his own name on the scoresheet midway through the first half to send the hosts in 2-1 up at the break.
Adam Lecky made it 3-1 in the 56th minute but Glenavon came roaring back with a goal from James Singleton and the fullback also had a goal disallowed for offside before Andrew Mitchell got on the end of a flick on by Gary Hamilton to make it 3-3 with five minutes to go.
A draw would have been the least Glenavon deserved but it was not to be as Ballymena clinched a second place finish for the first time in almost forty years.