MK Dons booked a place in the Southern Section semi-finals of the Johnstone's Paint Trophy, while Hereford and Norwich also progressed.
Paul Ince's Dons have their eyes on promotion from League One, but they would also relish a repeat of their 2008 success in the Football League trophy.
They made light work of Northampton at Stadium:MK as they recorded a 3-1 win, with all of the home side's goals coming in the first half.
Hereford shocked League One Leyton Orient with a 3-2 victory on penalties at the Matchroom Stadium.
Orient had only taken the game to spot-kicks as Jason Demetriou's last-gasp equaliser snatched a 1-1 draw in normal time.
Swindon went out on home soil after losing 5-3 on penalties to Norwich following a 0-0 stalemate.
Southampton play Charlton at St Mary's on Wednesday in the fourth semi-final of the Southern Section.