Mark Roberts's last-gasp header earned Stevenage a point as Graham Westley returned to his former stomping ground with new club Preston.
Patrick Agyemang threatened early on for the hosts when he cut inside from the right but could only fire over.
Iain Hume looked to have won it for North End when he slotted calmly past Boro keeper Chris Day.
But Roberts rose highest to head home Michael Bostwick's corner in the fourth minute of stoppage time.
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Preston manager Graham Westley told BBC Radio Lancashire:
"I thought we were by far the better side throughout the 90 minutes. We passed the ball well and carved out a lot of good moments.
"The 1-0 scoreline would have been well deserved had we held on at the end.
"There's a sense of purpose about the team, there's more understanding in the team of what's wanted and you can see a lot of progression in the performances in the last couple of games.
"If you look at the energy levels of the team in the second half, it says everything about the professionalism of the players."
Stevenage manager Gary Smith told BBC Three Counties Radio:
"I thought we deserved more than that for our general play.
"The guys showed a fantastic attitude throughout. Competitively we were the more dominant and the more physically capable.
"For good periods in that first half we had good territorial advantage and maintained good pressure.
"You have to score when you've got that momentum in the game."