Barry Fry, new owner of The Posh, is still waiting to celebrate a first outright win.
But he so nearly snatched it against ambitious City with an equaliser from enterprising substitute Richard Logan.
City, who had controlled the first half, were rocked by Peterborough's fightback.
Following up from their point at Oldham on Saturday, Posh were pleased with the draw but have now gone nine games without a win. It could have been so very different if they had not missed a third minute penalty.
Bristol City were dithering over clearing a corner when Mark Arber stumbled as he was pushed in the back. He dusted himself down to take the penalty which he tried to place inside the keeper's left-hand post.
The delivery was as slow as a second class stamp and Steve Phillips dived and collected the ball with time to spare.
It was a let-off for the Robins but the goal which saw them go ahead midway through the half was even softer.
A ball was played across the field to Brian Tinnion and with limited options open he tried a low shot from 35 yards.
Peterborough keeper Mark Tyler failed to react as the ball sped past the bodies in front of him.
It was the incentive City, who had won the previous four games between these clubs, needed and they ran the game for the rest of the half.
If Lee Peacock and Joe Burnell had not spurned two wonderful crosses from the Australian Luke Wilkshire by heading off target the result would have been settled by half time.
At the break though Fry still sensed he could salvage things. In a typically bold move he brought off a defender, Simon Rea, and sent on Logan to spearhead his attack.
There was an added determination too about a reshuffled back four and Peterborough, who had been all one touch and lightweight, began to worry the West Country side.
They were so close to a 65th minute equaliser when Leon McKenzie burst between two defenders with an angled shot which came back off the inside of the far post.
Another chance came and went when a mistake by Tony Butler let in McKenzie but a tame shot went straight into the arms of the keeper.
But a goal had to come and it did in injury time. It was schemed by Steve Thomson, crossed by Chris Kanu and volleyed in by Logan.