James Constable grabbed United a share of the spoils before being sent off after Chris Wilder's men conceded their first away goal of the season in a 1-1 draw.
Oxford had gone 408 minutes without letting in a goal on their travels when David Artell headed in his first-half opener for Crewe, but Constable levelled on the rebound after the break and then got his marching orders with three minutes to go to mark his 100th game in memorable fashion.
The visitors had looked impenetrable with Crewe restricted to a long-range Lee Bell effort and a Shaun Miller free-kick which rattled the side-netting, but Artell rose unmarked to convert Ashley Westwood's 38th-minute corner kick.
The Railwaymen should have extended their lead when Shaun Miller played in Clayton Donaldson but keeper Ryan Clarke did well to palm away his shot.
But United levelled in the 70th minute when Tom Craddock caught Crewe on the break and played in Constable who netted at the second attempt after a good save from Rhys Taylor.
Crewe thought Miller had netted winner, but after consulting with his linesman referee Geoff Eltringham rightly ruled the striker offside. Constable saw red with three minutes to go after picking up his second yellow for a late foul on Matt Tootle.