Peterborough striker Peter Godden scored twice in seven minutes and beat Scunthorpe to claim second place in the first division.
Godden scored a small cross from Colin Daniel in the 51st minute and added a second as his shot went through Scunthorpe keeper Jak Alnwick's hand.
Ryan Colclough had Scunthorpe's best chance, forcing Aaron Chapman to make a good save just before half-time.
Posh second place from Barnsley, who beat Luton 3-2 earlier in the day.
Peterborough reacted well to the 4-0 defeat of Barnsley last weekend, with Godden adding nine points to his record this season, making him the league's top scorer.
Scunthorpe struggled for a lot of chances despite being in control of most of the game, leaving them in 13th with just four wins in 13 games.