Swindon made two early first half subs after injuries with Ifil replacing Morrison, and then a few minutes later Kennedy replaced Robson-Kanu.
Obika gave Yeovil the lead on 33 minutes with a lob over Phil Smith to make it 1-0.
After the last 3 games this was a poor preformance by Swindon who rarely managed a shot on target all game. Swindon now drop down a place to 16th, and are once again only 2 points above the relegation zone.
