Rendell was one of 12 players put on the transfer list by manager Darren Ferguson at the end of last season but was on hand to bundle in a late winner.
Under-18 midfielder Jay Davies gave Posh the lead when he curled a free-kick into the top corner but Shane Fox levelled for the non-league side midway through the first half.
But Rendell grabbed a late winner to cap a third straight win for Posh ahead of the visit of Aston Villa on Saturday.
Source: Team_Talk