The two sides have already met in Sky Bet League One this season, on October 17, with Posh taking the 2-0 win at the Weston Homes Stadium. Last season, Oxford won two of the three meetings between the teams; they won the Carabo Cup first round tie and their home League One fixture in August 2019.
The tie will take place over the weekend of November 7. Due to Covid-19 restrictions, all matches will be played behind closed doors.
BT Sport and the BBC will be awarded broadcast rights for 16 of the first round matches, with the remaining 24 made available for livestreaming by the host clubs.