The classy wide man expertly turned in a low Russell Martin delivery to complete a stunning second-half revival and ensure Posh did not enter the record books for all the wrong reasons.
An eighth successive match without victory would have made it the worst start to a season in the club's history and that looked on the cards as Reading bossed the opening period.
Iceland Under-21 international Gylfi Sigurdsson pulled the strings for the Royals. He broke the deadlock with a glorious 25-yard free-kick on the half-hour and then turned provider when Wales international Simon Church doubled the lead with a free header four minutes before the break.
But any thoughts of a cruise to victory were quickly smashed to smithereens as Posh returned with much-needed fire in their bellies.
Posh boss Ferguson sent on midfielders Dean Keates and Lee Frecklington in a bold interval double substitution and his side quickly clicked into gear.
Craig Mackail-Smith needed only three minutes to cut their arrears when nodding home from a Paul Coutts corner and strike partner Aaron Mclean soon hauled them level with a power-packed 54th-minute drive after Boyd had led a rapid breakaway.
And that is the way it stayed until Boyd's late contribution at the end of an excellent passing move turned one point into three.
Ferguson said: "It feels great to have got the monkey off our backs.
"The lads could have gone one of two ways in the second half. They could have hidden and gone under but they showed immense character to turn things around and pick up a great result.
"I always felt we would have a chance if we could score the first goal in the second half and that's the way it turned out.
"The fans were absolutely unbelievable and they played a big part in getting us through. Hopefully this can now be the turning point of our season."
There was still time for drama at the other end after Boyd's winner with Posh goalkeeper Joe Lewis required to pull off a fine save from substitute Noel Hunt before fellow replacement Jimmy Kebe headed wide from the resulting corner.
Reading chief Brendan Rodgers admitted: "There is no way we should have come out of the game with anything less than three points.
"We were excellent in the first half when we scored two goals and could easily have led by three or four.
"We knew Peterborough would have to change their system to stop us playing in the second half, but we failed to match them up and were somewhat tactically naive.
"The game sums up our season and will hopefully act as a wake-up call."