Two goals from Player of the Match Stephanie Roche set them on their way before Aine O'Gorman, Karen Duggan, Becky Watkins and Tiegan Ruddy all added one apiece to seal the win.
This was game that surprisingly started slowly. Momentum for either side was absent in the opening 45 minutes as concentration levels remained high from the first whistle to the signal that the half was over.
O'Gorman did attempt to shake things up when drifting inside but her drilled shot flew wide. And Eleanor Ryan-Doyle lacked the necessary power with a header from inside the penalty area.
Cork did not create any chances of note - Sophie Liston shooting over from distance - but they would have been happy with their overall play as they matched the League champions stride for stride.
It was a different scenario just seconds into the second half when Roche raced onto a through pass from Lucy McCartan to neatly past Cork goalkeeper Maria O'Sullivan.
Cork had barely caught their breath after conceding that goal when Roche pounced again. The experienced striker found herself in the right spot to slot in from a pass back from Alannah McEvoy and that was 2-0.
Ronan Collins knew that his team needed to respond so he introduced experienced midfielder Katie McCarthy. But finding a way past the Peamount defensive wall of Niamh Farrelly and Claire Walsh looked like Mission Impossible in this game.
Peamount kept the pressure on and on 68 minutes Cork captain O'Sullivan pulled off a fantastic save to deny McEvoy. However, she was unable to stop O'Gorman from scoring the third goal of the game on 76 minutes.
Duggan then added the fourth goal by heading in from close range after Cork failed to clear a corner kick from Peamount. And substitutes Watkins and Ruddy added their names to the scoresheet with two late goals.
That was it for the 2020 season as Peamount claimed glory and cap off a fantastic year as double winners.
Cork City: O'Sullivan; Foley, McNamara (Walsh 82), Burke, O'Brien (S McCarthy 82); Liston (Seward 82), O'Mahony, Cassin, Noonan; Dring (Shine 72); Egbuloniu (K McCarthy 57).
Peamount United: Reid-Burke; O'Callaghan, Walsh, Farrelly (Doherty 84), Beirne (Doyle 79); McCartan, Duggan; O'Gorman, Ryan-Doyle (Watkins 79), McEvoy (Smyth-Lynch 70); Roche (Ruddy 84).
Referee: Claire Purcell.