A Lee Tomlin penalty in extra-time injury-time saw Peterborough edge past Stevenage in the Carling Cup.
David Ball headed home from close range to open the scoring for Posh before Stacy Long levelled from 18 yards out.
Ball restored Posh's lead from the edge of the box and Michael Bostwick sent the game into extra-time with a superb 25-yard effort.
George Boyd scored from range for Posh and Chris Beardsley headed a leveller before Tomlin's winner.
With the 120 minute mark approaching, Jon Ashton fouled former Stevenage player Boyd in the area and Tomlin sent Alan Julian the wrong way to seal the sides' first ever competitive meeting.
VIEWS FROM THE DRESSING ROOM
Stevenage manager Graham Westley told BBC Three Counties Radio:
"The goals were sloppy, unnecessary, really disappointing and totally uncharacteristic.
"They were a sign perhaps that we've got a lot of work to do to get our team and squad attitude back in the right place because to concede four goals at home is a real disappointment.
"We're prepared to put in the graft, we're prepared to learn and take the punches on the chin and come back stronger, it's what we do here."
Peterborough United manager Darren Ferguson told BBC Radio Cambridgeshire:
"Some of the football we played was absolutely superb but we just couldn't get the second goal ahead.
"We've got players that can produce a bit of magic to win a game.
"Lee Tomlin's played a great ball to George (Boyd) and it's a blatant penalty, and Tomlin's stuck it away."
Stevenage 01 Julian 02 Wilson 03 Laird 04 Charles 05 Ashton 06 Edwards (Winn - 109' ) 14 Roberts 25 Henry 08 Long (Shroot - 109' ) 24 Bostwick Booked 26 Harrison (Beardsley - 90' ) Substitutes 11 Myrie-Williams 32 Shroot 09 Madjo 10 Reid 12 May 17 Winn 20 Beardsley Peterborough 28 Jones 02 Little 03 Basey (Alcock - 105' ) 04 Bennett Booked 05 Zakuani Booked 14 Rowe 16 Tunnicliffe (Wootton - 76' ) 23 Frecklington 08 Tomlin 09 Ball (Taylor - 120' ) 10 Boyd Substitutes 13 Day 06 Wootton 27 Alcock 29 Ntlhe 17 Newell 20 Taylor 25 Ralth