As expected, Leon Britton returned for the suspended Darren Pratley, whilst Stephen O'Halloran was preferred at full-back in place of the injured Fede Bessone.
Swansea clicked into gear straight from the kick-off and Britton had a shot blocked by Bobby Hassell in the sixth minute before the ball ran to Owain Tudur-Jones who blasted over the bar from close-range.
Barnsley broke away and Miguel Angel Mostto forced Dorus de Vries to leap to his left to push away a stinging shot as the Tykes started to string some passes together.
A free-kick from Hugo Roberto Colace had de Vries stretching as the visitors were dangerous on the break.
Barnsley keeper Heinz Muller pulled off a tremendous double save as first Thomas Butler and then Gorka Pintado fired goalwards with just four minutes of the first half remaining.
Barnsley went ahead in the 49th minute when Jamal Campbell-Ryce broke away from the halfway line and out-paced the Swansea defence.
When his shot was turned away by de Vries, Jon Macken was on the spot to side-foot home.
There was a stunned silence when referee Graham Horwood pointed to the spot five minutes later following a Campbell-Ryce corner indicating a handling offence by Ashley Williams.
Campbell-Ryce coolly slotted the ball into the corner to double his side's advantage.
The Swans were back in the game in the 66th minute when a mistake let Scotland free and he thundered a shot into the net before Muller could move.
The goal sparked the Swans into life and they began to open up the Barnsley rearguard with both Scotland and Jordi Gomez forcing saves from Muller.
The equaliser they deserved came in the third minute of time added on when Scotland crashed his second into the net after being allowed to run free into the area.