But McGleish was then at the centre of the incident that provided the afternoon's main talking point when he looked to have handled after dropping back to help out in defence as the Cobblers defended a corner just before the break.
Despite a bright opening with Lloyd Opara lively on his first full start on loan from Cheshunt and bringing an early save out of Cobblers' keeper Lee Harper, Posh found themselves chasing the game when Sean St. Ledger dwelt too long on the ball and was dispossessed by McGleish who went on to slot a 21st minute shot beneath the body of Mark Tyler.
After losing influential skipper Dean Holden through injury, Posh battled back and 20 year-old St. Ledger almost made amends seeing a fierce drive deflected behind for a corner. Then, as home pressure continued, referee Andy Penn waved aside vigorous appeals for a penalty after McGleish was claimed to have deflected another St. Ledger effort with his hand.
Play became increasingly scrappy on a bobbling surface and Northampton, with 20 year-old Luke Chambers impressive, fell back to tighten their grip and achieve a 20th clean sheet of the campaign.
Posh's best second half hope was Paul Carden, who twice tested Harper from long range, before manager Steve Bleasdale replaced in-effective top scorer Danny Crow with Ryan Semple in a vain bid to find a way through.
With just one point from their last four games Posh's hopes of involvement in the play-offs are beginning to stutter.