Chris Whelpdale, Sergio Torres and Russ Martin netted the goals for Posh, and Ferguson felt they deserved the win despite a late rally from the Os.
He said: "We got the win after a home defeat although in all honesty in the second half we were very, very poor.
"We were hanging on in a game in which we were very comfortable.
"We were hanging on but we got three points and at this stage of the season that is the main thing.
"We went in 3-1 up at half-time and were very happy but in the second half we couldn't get out, keep the ball and were very ragged at times."