David Ajiboye netted a late winner to secure a 4-3 win in the second game after an own goal from Matthew Platt provided to be the difference in the first 90 minutes as Darren Ferguson's men warmed up for the new campaign with back-to-back wins over Sky Bet League Two side Notts County at the Weston Homes Stadium.
Posh made a bright start to the game with Chris Conn-Clarke taking advantage of a poor defensive pass only to send his effort well wide of the target.
Jed Steer made a routine stop on three minutes to keep out Jodi Jones while at the other end, Donay O'Brien-Brady curled a shot just wide of the upright.
Steer made a good stop to keep out Jatta on 32 minutes, the experienced custodian pushing the low strike around the post.
On 42 minutes, Conn-Clarke fired a free-kick over the crossbar before the half-time whistle was blown.
The deadlock was broken on 62 minutes and it was an own goal from Matthew Platt, who could only divert a Conn-Clarke cross past his own keeper.
Jack Sparkes fired wide from 25-yards and Conn-Clarke saw a volley held as Posh went in search of a second goal, which proved elusive.
The second game, with both sides fielding different XIs, started quietly with the first opportunity arriving on the quarter-hour mark as McGoldrick headed wide from a set-piece.
On 18 minutes, the Magpies opened the scoring as MCGOLDRICK used his experience to create the space and then found the bottom corner with a clinical finish.
Cian Hayes fired over after good work from David Ajiboye on 21 minutes before Posh drew themselves level as Ollie ROSE squeezed a header from a Harley Mills corner past Slocombe.
Odoh fired straight at Slocombe moments later after a quick counter attack before Posh were awarded a spot-kick as Hayes was felled in the box allowing Malik MOTHERSILLE to convert from 12-yards.
Mothersille dragged a shot wide of the far post on 36 minutes after good work from Odoh before the referee Neil Hair concluded the first 45 following no more incident.
Three minutes after the re-start, Posh should have added to their tally as Crichlow and then Ajiboye produced good passes with Mothersille hitting the post on the stretch from close-range.
On 53 minutes, Posh did add a third goal and it was MOTHERSILLE with it, he raced onto a pass from a Trialist and curled the ball past Slocombe.
Hayes fired wide after good approach play from Ajiboye before the visitors were awarded a spot-kick as Rose was penalised for a foul. MCGOLDRICK stepped up and sent Bilokapic the wrong way from 12-yards.
On 78 minutes, the visitors equalised as EDWARDS was allowed time and space to slam home from close-range after a bit of indecision in the Posh defence.
Posh grabbed a winner two minutes from time with arguably the goal of the game, Mothersille cutting inside and squaring for Hayes, who in turn picked out the onrushing AJIBOYE who made no mistake with a fine left-foot finish.
Posh: (1st game): Steer, Curtis (sub Sumnall 60min), Wallin, Fernandez, Sparkes, O'Brien-Brady, Collins, Conn-Clarke, Randall, Poku, Jones.
Posh (2nd game): Bilokapic, Dornelly, Mills, Crichlow, Rose, Hayes, Trialist A, Trialist B, Odoh, Ajiboye, Mothersille.
Unused subs: Kamara, Trialist C, Fox, Beech, Changunda, Mendonca.
Game One: Peterborough United 1-0 Notts County
Game Two: Peterborough United 4-3 Notts County