Jonathan Russell equalized Ricky-Jade Jones' early goal as Barnsley and Peterborough settled for a 1-1 draw.
Conor Hourihane earned his first point as Barnsley's permanent head coach, while Peterborough ensured their safety with the result at Oakwell.
After a cautious start, Peterborough's Jed Steer was the first goalkeeper in action as he pushed Adam Phillips' shot onto the post.
Peterborough took the lead in the 17th minute with a swift counter-attack. Abraham Odoh set up Jade Jones, who scored from close range.
Barnsley pressed for an equalizer and found success just before half-time when Russell scored with a precise shot into the top corner.
Russell came close to scoring again in the second half but narrowly missed the target.
Although the game had quiet periods, both teams had opportunities to snatch a win.
Davis Keillor-Dunn had a chance to win it late on, but he couldn't hit the target with his volley.