The best chances all came in the second half, with Stuart Elliott guilty of wasting the most clearcut of them. Just after the hour mark Jon Walters put him clear, but he pulled his shot just wide when one-on-one.
Nearly 10 minutes later substitute Martin Reeves crossed in to Walters, but his header was stopped on the line by Oxford 'keeper Andy Woodman, who knew little about the save.
Jamie Forrester then came closest out of everyone, working his way into the area and smashing his shot against the crossbar.
In the dying minutes Ian Ashbee was stretchered off to end what was an encouraging yet frustrating day of football.
City line-up (4-4-2): Fettis; Joseph (Melton 56), Whittle, Anderson, Delaney; Appleby (Reeves 45), Ashbee (Smith 88), Keates, Elliott; Walters, Forrester.
Un-used subs: Musselwhite, Dudfield.