Swindon secured victory over promotion rivals Yeovil to move up to third in League One.
Darren Ward scuffed wide for Town while Glovers striker James Hayter skewed his volley over the bar in the first half.
Swindon broke the deadlock in the second half when Adam Rooney smashed home from the penalty spot after keeper Marek Stech had felled Gary Roberts.
Sub James Collins doubled their lead in the last minute of injury time when he raced clear and struck under Stech.
The result dents Yeovil's automatic promotion hopes as they slip to seventh in the table, four points off second-placed Brentford.
Gary Johnson's Glovers looked the more lively in a cagey first half hindered by the bobbly Huish Park pitch.
Midfielder Joe Edwards saw his shot loop over the bar, while Hayter skilfully controlled the ball with his head before hitting well over.
At the other end, Rooney failed to latch on to a long ball from captain Alan McCormack and Ward knocked just wide in a crowded penalty area.
Swindon improved after the break and Gary Roberts thought he had netted the opener but his rising strike was disallowed after a foul was committed in the build-up.
Yeovil's top scorer Paddy Madden was twice thwarted by some excellent defending from Nathan Thompson, and Stech was forced in to two athletic saves before conceding the penalty.
The Czech Republic Under-21 international caught Roberts on the edge of the area and Rooney stepped up to convert.
And Swindon put the result beyond doubt, as Collins rushed forward on the counter attack and coolly slotted home.
VIEWS FROM THE DRESSING ROOM
Yeovil Town manager Gary Johnson told BBC Somerset:
"I thought in the first half we were pretty tight and got in with some good play.
"Paddy [Madden] had a good chance, and James Hayter, and that would have settled us.
"We've got some inexperienced players and they showed their inexperience on a big stage.
"On the big occasion they weren't up for it."
Swindon Town manager Kevin MacDonald told BBC Wiltshire:
"I'm delighted - especially for the players and the fans who travelled down here.
"They got behind the lads and you can see the passion between the players and the fans.
"We can play better. We've played better and lost. But sometimes winning ugly is important.
"It was a bit untidy in the second half and a little bit nervy, but when we scored the first we got a lot better."