It could not have come at a better time as the Glovers were trailing to the struggling O's with time running out and, despite dominating the second half, had failed to put keeper Glyn Garner under a great deal of pressure.
Orient dominated the first half and fully deserved their 31st-minute goal from Ryan Jarvis that threatened the play-off hopes of the home team.
Soon after his goal, Craig Easton missed a golden opportunity to make it 2-0 and Yeovil boss Russell Slade admitted: "I had probably eight players who weren't really at the races in the first half and we had to do something about it.
"I made some changes at half-time but several of the others who stayed on upped their performance to turn things around."
Yeovil have two former Premiership strikers in Marcus Stewart and Lee Morris, and they were the men who were taken off at the break to be replaced by the younger legs of Anthony Barry and Darryl Knights.
Their pace put Orient under much more pressure and, with 13 minutes left, their constant attacking paid off when Nathan Jones was brought down in the box by Adam Tann and man-of-the-match Wayne Gray scored from the spot.
Yeovil were now in full cry and, in the 83rd minute, they got the winner.
Arron Davies crossed from the right and the ball skidded off the foot of John Mackie as he attempted to clear, for the own goal that won the game and cemented Yeovil's place in the play-off positions.