Britt Assombalonga scored twice in as many second-half minutes to secure Posh's grip on the play-off places, extending their lead over the Dons to six points while they still have a game in hand.
It was a crucial win after three defeats in their previous four games with Assombalonga tucking home Josh McQuoid's cross in the 58th minute and then scoring from the penalty spot.
And while Ferguson admits his side still need to find consistency in their results, he applauded his side's performance when it mattered.
"I have to give credit to the players because they put the performance on," he said.
"We know the problem this season has been consistency but the one thing we have done well is beat most of the teams that we're challenging with &£91;for a play-of spot&£93; and that is something we have to take great confidence from.
"I wasn't happy with Britt first half as he gave the ball away too much but second half he did what he does best.
"His first was a real goalscorer's goal and then he showed great composure with the penalty. He's by no means the finished article but any striker who can get 30-35 goals a season in any league is some going. The front two gave them problems all afternoon but as a team it was a professional performance and I felt we thoroughly deserved to win.
"We generally do well in March but this is the worst March we've had in this league so this was a big result."