Burton Albion lead Oxford United at half time after Lucas Akins's strike just before the break.
Alex MacDonald went into the referee's notebook for a poor challenge on Joe Riley early on as the affair became fiery.
It was Joshua Ruffels who came the closest from scoring around 10 minutes before the break after his low shot was saved comfortably by the Burton goalkeeper.
Burton took the lead moments before half time as Stuart Beavon squared the ball to Lucas Akins, who finished well with his right foot to put the away side 1-0 up.
