Jim Smith enjoyed a winning start to his second spell as Oxford manager as they saw off Peterborough. New signing Tcham N'Toya struck the winner on his debut, hitting an angled shot beyond Mark Tyler in the 67th minute to secure the three points.
The margin could have been greater but Tyler made a series of fine saves, in particular from a Steve Basham header.
James Quinn had Posh's best chance of getting a leveller, but his long-range effort was saved by Andrea Guatelli.
Oxford Utd: Guatelli, Mansell, Willmott, Roget, Robinson, Quinn, Smith, Hargreaves, Burgess (Brooks 86), N'Toya (Horsted 73), Sills (Basham 53).
Subs Not Used: Turley, Ashton.
Goals: N'Toya 67.
Peterborough: Tyler, St. Ledger, Arber, Bolland, Kennedy, Newton, Gain, Carden, Day (Opara 81), Crow, Logan (Quinn 40).
Subs Not Used: Harrison, Farrell, Ryan.
Booked: Tyler.
Att: 7,486.
Ref: R Beeby (Northamptonshire).