Tony Naylor gave Bobby Gould's side the perfect start in the first minute when he latched onto Mike Duff's pass to fire the home side ahead.
However, it didn't last long, with Mike Sheron levelling the scores on 17 with a low shot past Steve Book.
And Barnsley took the lead on the hour mark when Bruce Dyer swooped to head The Tykes into the lead.
Gary Jones sealed the points in the final minute to give the Oakwell side a vital 3 points as they leapfrog Notts in the table and go to 15th while The Magpes slip to 16th.
Brentford 0-0 Colchester United (Abandoned At Half Time)
A goalless first half at Griffin Park before the game was called off due to a frozen pitch. Both sides had chances in the first half, but neither could find the net.