Derry City scored three goals in the second half to comfortably seal a place in the EA Sports Cup semi-finals.
Patrick McEleney's skilful backheel set up Stephen McLaughlin to net a 48th-minute opener and a fine Ruairi Harkin shot made it 2-0 nine minutes later.
McEleney was the creator again as his ball gave Michael McCrudden the opening for Derry's third on 61 minutes.
UCD had full-back Sean Harding sent-off for a push on McLaughlin but David McDaid's penalty struck a post.
After an even first half, Derry's display after the break was convincing, which was in contrast to their disappointing 2-2 draw at UCD in the Premier Division three days earlier.
City boss Stephen Kenny made nine changes from Friday night's game with only McEleney and Eddie McCallion keeping their places in the starting line-up.
Eugene Ferry, Gerard Doherty's replacement in goals, pulled off a good save from Robbie Benson in the first half.
But it was UCD's keeper Ger Barron who had all the problems after the break.
He was beaten by McLaughlin's lovely finish after Ryan McBride and McEleney created the chance three minutes into the half.
Barron then tipped away a McEleney shot but he had no chance with Harkin's super 25-yard strike in the 58th minute.
McEleney, who had an outstanding game, provided the delicate flick for McCrudden to shoot low into the corner for City's third.
Derry's poor penalty record continued when McDaid failed from the spot in the 74th minute but Derry were already home and dry.