The hosts took a 12th-minute lead through Steven Schumacher and they looked set to go on and seal the win, but Oxford responded to stay in control at the summit.
Experienced striker Dave Kitson struck in the 89th minute to rescue a point for Chris Wilder's men, but the draw means that second-placed Chesterfield will go top if they beat Newport County on Sunday.
Scunthorpe United also gained ground on the leaders thanks to their 3-1 victory over struggling Torquay United.
Sam Winnall and an Anthony O'Connor own goal gave the hosts a 2-0 lead at half-time before Hakeeb Adelakun made it 3-0 in the 61st minute.
John Marquis pulled a goal back for Torquay late on, but they remain in the bottom two.
Meanwhile, Southend United were held to a 1-1 draw at home to Cheltenham Town after Kevan Hurst's goal was cancelled out by a last-minute strike by Matthew Richards.
Burton Albion picked up a third consecutive league win when they triumphed 1-0 at Plymouth Argyle, while Rochdale remain one place above them in fifth after they were held to 0-0 by York City at Bootham Crescent.
At the bottom, Northampton Town moved off the foot of the table thanks to a 1-0 victory over Accrington Stanley, who stay dangerously close to the relegation zone themselves.
Exeter City were unable to close in on the play-off places as they drew 2-2 with Bury, but Dagenham and Redbridge's 2-0 win over Wycombe Wanderers saw them jump up to eighth.
Mansfield Town suffered a sixth league defeat in a row as Morecambe claimed a 2-1 win while a 3-0 home victory over AFC Wimbledon kept Bristol Rovers just above the relegation places.
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