David Noblle, Kari Arnason, Johnny Mullins and Ben Pringle all bagged goals in the final 15 minutes of the first half as a dominant Rotherham shell shocked their hosts.
“It’s a great night,” said the Millers boss speaking to the clubs website. “It’s a difficult game and that doesn’t change just because you come here and win 4-0.
"Goals change games and I don’t think there was much in the game in the first 15 minutes but we’ve identified their system, and we made changes by putting two players right out wide and taking advantage.
"Oxford are unfortunate with the first goal as it takes a deflection but I was more pleased with how we stretched the game after that for the other three. They had three at the back and we went wide on the right and wide on the left which left Alex Revell one-on-one with Duberry through the middle.
"During the second-half we spoke about keeping our shape and all they’ve managed I think is one cross into the box really.”