St Mary’s recovered from early penalty disappointment to see off AFC Craigavon on a 4-2 tally.
James Cullen had a spot-kick attempt saved before a slice of good fortune allowed the Saints to move in front off an own goal.
Sean Brady’s strike doubled the St Mary’s advantage but AFC hit back and a goal late in the half handed the hosts hope of a fightback.
However, another Brady finish - this time courtesy of a decisive header - increased the St Mary’s lead to 3-1.
Kieran McCann, back with the Saints, marked his return to the club with a volley assist for Luke Carvill to convert.
AFC cut the deficit to 4-2 before the final whistle - with Carvill, Brady and Cullen each close to adding to St Mary’s control.