Marcel Cas returned to the right wing. The bench of Pettinger, Parker, Young, Soames and Hockless was one of the most inexperienced seen in recent times.
Town were slow to get out the blocks with most attacks consisting of hopeful punts up to the starved Michael Boulding and Jonny Rowan.
Peterborough were looking by far the better team and fully deserved the opener on 18 minutes. Adam Newton took advantage of Mike Edward's backing off to curl a superb effort into the far corner of the goal leaving Davison with little chance.
The goal failed to spark Town into life, McKenzie should have done better than firing over after a misplaced Bolder pass.
Aidan Davison kept his team in the game just before the break. Andy Clarke found David Farrell unmarked. Farrell's volley was sweet enough but the veteran 'keeper launched himself to tip around the post.
Town came out in a better manner for the second half, Rowan was at the heart of some clever football which failed to produce much.
Rowan set Campbell up with a good shooting chance on 55 minutes, the midfielder was fouled though with the ref waving play on. From that Peterborough almost doubled their lead, only the post saving Town.
Chris Bolder made way for Graham Hockless around the hour mark, the pint sized midfielder brought some much needed creativity to the game.
Despite some clever play from Hockless, Town were unable to break down the Posh defence. In fact the visitors looked more likely to score, Clarke took of an dangerous runs on several occasions with one intention.
Town's equaliser on 81 minutes was rather fortunate. Edward's long clearance was misjudged by Legg and Rea leaving Boulding to nip and fire past Tyler for his fifth goal of the season.
David Soames replaced Jonny Rowan with a few minutes to go. 'Digger' had missed most of the pre-season with injury. Boulding and McKenzie both had weak penalty appeals turned down by referee Paul Danson before the final whistle.
Man of the Match: Aidan Davison. Superb performance from the 'keeper. Several saves kept Town in the game, with the Farrell one simply outstanding.
Grimsby: Davison, McDermott, Ford, Crane, Edwards, Cas, Groves, Bolder (Hockless 62), Campbell, Rowan (Soames 87), Boulding. Subs: Pettinger, Parker, Young.
Peterborough: Tyler, Gill, Rea, Legg, Jelleyman, Newton, Boucaud (Thomson 89), Shields, Farrell, Clarke, McKenzie. Subs: Scott, St. Ledger, Green, Fotiadis.