Brendan Clarke saved City’s first penalty from Garry Buckley and Pat’s converted all five of theirs to join Galway, Dundalk and Shamrock Rovers in the last four.
Ross Gaynor was returning for the home side after a hamstring injury and boss John Caulfield, with one eye on Friday’s big clash with Shamrock Rovers, made nine changes to the side that narrowly defeated Limerick on Saturday.
St Pat’s boss Liam Buckley also gave a few of his fringe players a chance to impress as he made six changes to the side that surprisingly lost to Bray Wanderers on Saturday.
In a lively opening, City keeper Alan Smith made a good stop the tip Conan Byrne’s free-kick around his post in the 19th minute before Jason McGuiness missed a sitter from the resultant corner kick, when he rose unopposed but headed over from six yards.
Kevin O’Connor then missed a gilt-edged opportunity to put the home side in front when Danny Morrissey found the recent signing but he put the ball wide when one on one with Brendan Clarke.
Caulfield replaced John O’Flynn with John Kavanagh at half-time and moved Danny Morrissey to his more familiar role up front and the switch almost paid immediate dividends when Rob Lehane found Morrissey but Clarke was quick off his line to deny the striker.
Pat’s hit the front on the hour mark when Smith misjudged Bermingham’s long cross into the box and Jack Bayly was on hand to head home at the back post.
The visitors lead only lasted four minutes however, when Rob Lehane’s snap shot from the edge of the box came back of the foot of a post and Liam Kearney side footed the rebound home.
With the home side now on top, Caulfield introduced Billy Dennehy and Mark O’Sullivan and Clarke made a good stop to tip over Lehane’s effort from 20 yards.
City lost Morrissey with what looked like a bad knee injury in the second half and Dennehy came closest to winner in the nine minutes of injury time resulting from that incident.
With extra-time failing to separate the sides, it came down to the penalty shoot-out where Clarke and Forrester made the difference as Pat’s kept their cool.
Smith, O’Shea (B Dennehy 66), Murray, McSweeney, Gaynor, Morrissey (O’Sullivan 76), Buckley, O’Connor, Kearney, Lehane, O’Flynn (Kavanagh 45).
Clarke, McCormack, McGuinness, Browne, Bermingham, Byrne, Chambers, Verdon (Brennan 91), Bayly (Markey 83), Langley, McGrath (Forrester 120).
S Grant (Wexford)