Milton Keynes 1 Swindon 4
A goal by John Paul McGovern on 41 minutes from 40 yards out opened the scoring for Swindon.
Easter equalised for Milton Keynes on 53 minutes with a penalty.
Paynter then went on to score two goals, and an own goal was enough to make it 4-1.
Swindon now go on to play Milton Keynes again in the league on Saturday, this time at home.