Joel Grant had given Town a 10th-minute lead at Oakwell but the Tykes were handed a lifeline 11 minutes before the break when James McAllister brought down Tomasz Cywka in the penalty area.
On-loan Nottingham Forest striker Marcus Tudgay stepped up to score from the spot and rescue a point for the home side but the Reds are now two points adrift at the bottom following Sheffield Wednesday's win at Watford.
Barnsley had the better of the early exchanges and Cywka and Paddy McCourt both tested Glovers stopper Chris Dunn before the visitors took the lead.
Grant got on to the end of Byron Webster's cross from the right and slid the ball into the empty net from 12 yards out with Jack Butland out of position.
Yeovil should have doubled their lead 10 minutes later when a Joe Ralls cross from the right found Joe Edwards whose shot from the edge of the area hit the post with Butland left rooted to the spot.
In their next attack, striker Ishmael Miller fluffed his shot from just inside the area when a second goal looked a certainty.
Barnsley got back into the match when referee Lee Probert pointed to the spot after McAllister tripped Cywka and Tudgay gave Dunn no chance to score his first Tykes goal.
Tudgay nearly went from hero to zero inside a minute when a cross from the right hit his leg but luckily for him went straight into the arms of Butland.
Just before half time the Barnsley fans thought they had taken the lead when Jacob Mellis' curling shot looked destined for the far corner but was cleared behind.
The hosts started the second half much better and a cross from the left by full-back Tom Kennedy in the opening minutes was just inches out of the reach of striker Marcus Pedersen.
Grant's clever dummy down the left started a move which stretched the Barnsley defence and ended when full back Luke Ayling blasted into the side netting.
In the 63rd minute, Barnsley substitute Jason Scotland's shot grazed the visitors bar.
Two minutes later, Yeovil thought they had retaken the lead when Miller bundled in a Grant cross from close range but referee Probert ruled that the striker had handled it.
Ten minutes from time a cross from Grant was headed back across the face of
goal by substitute James Hayter to Miller but the big striker put his header
wide from five yards.
A header from Barnsley substitute Jean Yves M'voto was brilliantly turned around the post by keeper Dunn in the closing stages before Yeovil turned defence into attack and a close range header by Grant went over.