It was a lively start to the game, with Larne denied by the woodwork in the opening two minutes when Sean Graham’s effort crashed off the crossbar.
The away side then broke the deadlock on seven minutes when they were awarded a penalty after MJ Kamara handled the ball in the box and O’Neill fired home the resulting spot kick.
After conceding, the Glens settled into the game and levelled when Larne’s defence were unable to clear Cooney’s long throw before Daniel Larmour nodded home.
The feisty and fast-paced tempo of the match continued with the home side reduced to 10 men when Tony Clarke gave Cooney his marching orders for a poor challenge on Graham.
In the final five minutes of the half, the Inver Reds went in front again with former Glens midfielder Gallagher’s shot from 30 yards finding the bottom left corner.
The league leaders extended their lead nine minutes after the restart when Tiarnan O’Connor controlled a goal kick and travelled into the box before crossing for O’Neill to steer home for his second of the evening.
In the 77th minute, James Simpson robbed Danny Amos of the ball and fed Cosgrove, who was able to convert to complete a successful night for Gary Haveron’s side.