The first-round fixture offers a repeat of last season's League One playoff semi-final which Oxford won by a 2-1 aggregate scoreline.
Match preview
Oxford are competing in the Championship for the first time this century after securing promotion via the League One playoffs.
The U's ousted Tuesday's opponents in the playoff semi-final, before they beat Bolton Wanderers at Wembley to return to the second tier for the first time since 1998-99.
Oxford made an impressive start to their Championship campaign, with Mark Harris and Cameron Brannagan getting on the scoresheet to fire the U's to a 2-0 win over Norwich City in Saturday's league opener.
They will now turn their attention to League Cup action, and the U's will be looking to avoid consecutive first-round exits after losing to Bristol City in the first round of last season's competition.
Tuesday's fixture will be the first EFL Cup meeting between the two sides since Oxford recorded a 1-0 victory in the first round in August 2019.
After experiencing disappointment in last season's playoffs, Peterborough are competing in League One for the third consecutive campaign.
Unfortunately for Peterborough's, their 2024-25 campaign began with a 2-0 home defeat against recently relegated Huddersfield Town.
The Posh were unable to produce a response after Huddersfield's Anthony Evans and Ben Wiles scored in the closing stages of the first period.
After beginning the new season with a defeat, the Posh will be hoping to build confidence with a strong performance in Tuesday's EFL Cup clash as they look to progress from the first round for the third year in a row.
Peterborough recorded a 2-0 victory against Plymouth in the first round in 2022-23, before they beat Swindon Town on penalties at this stage of last season's competition
Oxford United form (all competitions):
W
Peterborough United form (all competitions):
L
Team News
Oxford are unable to call upon the services of Will Goodwin, who has been ruled out for six weeks with an ankle problem.
Owen Dale is a doubt for Tuesday's fixture after being forced to miss the win over Norwich due to a minor injury issue.
Des Buckingham is likely to rotate his side for the first-round clash, and he could offer starting berths to the likes of Matt Ingram, Greg Leigh, Peter Kioso, Josh McEachran, Idris El Mizouni, Louie Sibley, Malcolm Ebiowei and Gatlin O'Donkor.
As for the visitors, they are without left-back Ryan De Havilland and midfielder Rio Adebisi due to their respective injury issues.
Peterborough captain Hector Kyprianou remains a doubt for the EFL Cup clash after sitting out the league opener with a knee problem.
Ferguson is likely to make changes for Tuesday's contest, and he could present starting spots to Nicholas Bilokapic, Romoney Crichlow, Donay O'Brien-Brady, David Ajiboye, Cian Hayes and Malik Mothersille.
Oxford United possible starting lineup:
Ingram; Kioso, Moore, Brown, Leigh; Ebiowei, El Mizouni, McEachran, Sibley, Placheta; O'Donkor
Peterborough United possible starting lineup:
Bilokapic; Curtis, Crichlow, Fernandez, Sparkes; O'Brien-Brady, Collins; Hayes, Randall, Ajiboye; Mothersille