Darren Ferguson's first-team squad struck three times in each half in front of a crowd of 1,573 which was a new best for Stamford's Zeeco Stadium.
Ivan Toney's second half double was backed up by strikes from Matt Stevens, Harrison Burrows, Niall Mason and Serhat Tasdemir.
But, despite the margin of the defeat, Stamford manager Graham Drury was 'pretty pleased' with the performance of his newly-assembled squad.
Drury said: "We did give three sloppy goals away - the penalty, free-kick and another at the end - but we've got five players away at the moment who are quite big for us and I've only had these boys together training for five hours.
"There's 16 new faces so I'm pretty pleased. I can't thank Peterborough enough for what they have done for our club.
"It's a good fundraiser for us, but it's also a fantastic exercise for my boys and I wish Peterborough all the best for the season. They look like they've got a quality squad this season.
"Our plan was to have building blocks with a clean sheet for 10 minutes, clean sheet for 20 minutes and we then conceded on 23 minutes.
"We conceded another on 33 minutes, but the one I was disappointed about was the one straight after.
"Instead of being a little bit compact and just trying to work our way back into it, they pressed us pretty quickly. We gave a sloppy ball away and then it was 3-0.
"Take away the three sloppy goals, we had more corners than them in the first half and had more attempts at goal, although maybe not on target.
"I thought we competed really well in the first half. It's always going to be disjointed a little bit when you're making changes but we got out of it what we wanted and I can't thank Darren Ferguson and Peterborough enough for what they have done.
"I'd like to thank all the Posh fans who have came and everybody who has attended. It was a fantastic crowd and an unbelievable attendance. Hopefully they have seen some encouraging signs from us."
Stamford's starting line-up included just four players - goalkeeper Dan Haystead, skipper Mike Armstrong, Josh Egginton and Jon Challinor - from last season.
They started brightly and came closest to breaking the deadlock in the opening exchanges when the lively Louis Danquah brought a fine reaction save out of Posh goalkeeper Conor O'Malley after a smart turn and shot.
Siriki Dembele posed Posh's main attacking threat in the first half with his searing pace and silky skills which created a good opening but the Ivorian blazed his shot over the crossbar.
Posh broke the deadlock midway through the first period when Harrison Burrows' fine play down the left saw his cross loop over Haystead for the lurking Matt Stevens to head home from close range.
Haystead produced a decent stop to deny Stevens his second before Posh doubled their lead just past the half-hour mark.
Dembele was the creator as his mazy run down the left was followed by a low cross which was dummied by Posh's record signing Mo Eisa for the in-coming Burrows to slot home.
A third Posh goal followed 60 seconds later as Niall Mason burst forward and, after a smart of inter-change of passes with Eisa, rolled his effort past the advancing Haystead.
Stamford responded with Challinor, who had seen a couple of decent efforts charged down, curling a sweet strike narrowly wide.
New signing James Hicks then got on the end of an inviting Danquah cross despite having his shirt pulled but his close range header was smothered by O'Malley.
Both sides rang the changes at the break but, despite Posh fielding an entirely different eleven, they continued to carry the greater attacking threat.
Idris Kanu missed a gilt-edged chance to make a four when he failed to convert a Jason Naismith cross from close range.
But the visitors did increase their lead further just before the hour mark when Toney stepped up to curl home a free-kick from the edge of the Stamford box.
Toney was then denied a second shortly after by a cracking covering clearance off the line by Charlie Ward.
But the one-time Newcastle United marksman didn't have to wait much longer to bag his brace after casually converting a penalty following Danque's foul on Kanu.
The League One side then wrapped up the scoring with 14 minutes remaining as Serhat Tasdemir robbed Sam Hill before racing clear and finishing with aplomb past replacement Stamford goalkeeper Dan Swan.
Posh: First half - O'Malley, Mason, Beevers, Blake-Tracy, Woodyard, Cooper, Burrows, Dembele, Eisa, Stevens, O'Hara.
Second half - Pym, Kent, Bennett, Naismith, Butler, Reed, Barker, Tasdemir, Kanu, Jones, Toney.