Byrne scored a hat-trick in Monday's 6-0 rout of Drogheda United to add to the goal he got in last week's 5-2 win over Derry City.
And he broke non-league St Patrick's CY's resolve just before half-time before a terrific strike from Keith Fahey and a third from Daryl Kavanagh eased Liam Buckley's side through.
But for Ian Bermingham heading off the line from St Patrick's CY's Mark Boland after they failed to clear Alan Murphy's corner inside two minutes, the Inchicore Saints, as expected, utterly dominated the game.
They bossed it from the start but it took 42 minutes to break the deadlock. James Chambers swept a ball wide right to McCormack who put Byrne in first time and he did the rest, casually shooting home with the outside of his right foot.
A stunning 25-yard strike from Fahey all but ended the contest seven minutes into the second half.
Four minutes later Fahey's sublime pass put Killian Brennan in to rattle a shot off the crossbar. Kavanagh added Pat's third goal on 87 minutes, firing a low drive past the excellent Darren McGarry and into the far corner.
© Irish Independent