Goals from Chris O'Grady, Liam Lawrence and Dale Jennings saw the Tykes leapfrog their Somerset hosts and secure back-to-back wins for the first time this season.
Both sides were locked on 32 points in the division's drop zone before the match and the occasion appeared to get the better of the nervy Glovers during a first half that lacked clear-cut opportunities.
Looking to build on Tuesday's impressive 3-1 win at Reading, the visitors settled quickest and threatened the Yeovil goal for the first time when O'Grady's effort was blocked.
Yeovil came within seconds of a shock win at league leaders Leicester before Kaspar Schmeichel's late equaliser four days ago, but their' first-half display had no resemblance to the mid-week performance that attracted so many plaudits.
The hosts, who had lost one of their last six matches before the relegation scrap, awoke from their slumber when Joe Ralls' teasing free-kick narrowly eluded Shane Duffy, but it was Danny Wilson's men who dictated proceedings during a poor opening period.
After striker Marcus Pederson limped down the tunnel after only 25 minutes, the introduction of Reuben Noble-Lazarus, who netted Barnsley's second at the Madejski Stadium on Tuesday, gave the visitors more potency in the final third.
O'Grady twice combined with his strike partner before the break, but the 20-year-old's first effort was blocked before he flashed a stinging shot narrowly wide.
Yeovil called Barnsley goalkeeper Luke Steele into action shortly before half-time after Joe Edwards and Kevin Dawson's smart free-kick routine teed up Manchester United loanee Tom Lawrence, but his shot was clawed over the bar.
Desperate to avoid a fourth consecutive draw, Yeovil started the second half brightly and Kevin Dawson - coming up against his older brother Stephen who captained the Tykes - produced a pin-point pass to Edwards seconds after the restart, but the midfielder could not get his shot away cleanly.
Barnsley snatched a deserved lead when O'Grady pounced on a weak defensive header by Bryon Webster to coolly lob the ball over the onrushing Marek Stech.
The Somerset side's dismal day took a turn for the worse shortly after the hour mark when former Sunderland midfielder Lawrence weaved his way past a couple of tackles before lashing an unstoppable effort into the bottom corner of the net.
Yeovil were given a lifeline with 20 minutes to go when defender Luke Ayling rifled Jamie McAllister's low cross into the net.
But the hosts paid the price for a drab display on home soil when O'Grady completed his timely brace after taking the ball around Stech, before Jennings prompted a mass exodus by rattling home Barnsley's fourth.