Barnsley lost at Oakwell for the first time this season as they went down 2-0 at home to bottom club Peterborough.
The Posh secured their first win at Barnsley since 2004 with two goals inside the first 11 minutes. Geroge Boyd put them ahead after two when he fired in after Ben Alnwick had made a superb one-handed save. Alnwick came to Barnsley's rescue twice more as Peterborough dominated then eventually scored the second through Tyrone Barnett's fine header.
Barnsley gradually got back into the game and almost halved the deficit when Craig Davies' superb 20-yard struck crashed against the underside of the bar.
The Reds had a lot of possession in the second half but failed to create many chances apart from a Stephen Dawson cross that substitute Marlon Harewood completely missed.