The game was arranged between the two clubs as part of the deal when Lloyd Opara joined Swindon in the summer from Grays on a free transfer.
Swindon's only goal of the game was scored by Rory Fallon in the first half.
Tonight Swindon are playing Cirencester Town, and on Saturday they travel to play Bristol Rovers, then next Tuesday evening Swindon play Southampton at the County Ground.