University of Limerick booked their place in the semi-finals as Shane Stack's last-minute piledriver gave them a 2-1 win over highly-fancied hosts Maynooth University.
Shane Dunne had put the home side in front just before the break after Maynooth had dominated most of the first half.
The Limerick side - defeated finalists last season - responded in fine style on the resumption and went on to take control of the game.
However, they had to wait until the 75th minute before Garbhan Coughlan pulled them level with a goal at the second attempt after his initial effort was blocked by Dunne.
That set the scene for the late drama, with Stack crashing in a fierce drive from 25 yards that came off the underside of the crossbar and bounced down over the goalline.
Limerick will meet holders UCD in this afternoon's semi-finals after substitute Ben Hanrahan struck the only goal with seven minutes remaining of a hard-fought quarter-final against Queens' University.
The decisive goal finally arrived on 83 minutes when Hanrahan got clear on the right to cut into the penalty area before scoring with a low drive.
A surprisingly sluggish UCC had Daniel Pender to thank for a 1-0 win over a dogged Trinity College side.
Pender struck on 30 minutes to set up a semi-final clash against DCU in what will be a repeat of last week's CUFL Premier Division semi-final, which UCC won 1-0.
Ross Taheny scored in the last minute of extra-time to give DCU a dramatic 3-2 win against NUI Galway.
Jack O'Connor had DCU in front on 63 minutes after Galway went a man down, with substitute Conor Melody receiving his marching orders.
A brilliant Maurice Nugent strike brought Galway level in the final minute of normal time.
Conor Barry put the Tribesmen ahead early in extra-time with another splendid goal but DCU grabbed a lifeline when Colm Callinan got the final touch in a goalmouth scramble.