Oxford made it seven Sky Bet League One games unbeaten as they claimed a 2-1 win at Rotherham.
Oxford took the lead in the 23rd minute out of nothing with Tariqe Fosu collecting the ball on the edge of the box and driving a powerful shot beyond the reach of Daniel Iversen.
Rotherham's response saw them unsuccessfully appealing for a penalty with Chris Cadden's block from Jake Hastie's goal-bound effort striking his own arm.
The Millers levelled in the 35th minute with Michael Ihiekwe finishing off a move which he started from central defence.
The defender's marauding run resulted in a cross coming in from Michael Smith and Ihiekwe was in position to bravely nod past Simon Eastwood.
Oxford retook the lead in the 57th minute with Fosu expertly finding Matty Taylor who guided his header beyond the reach of Iversen.
The visitors had opportunities to stretch their lead with John Mousinho's effort being deflected just over and Fosu striking the post in added time.