Jacques Maghoma's low shot 20 minutes from time brought them a first away point in 2013 after a barren run without a goal on their travels this year.
James Constable had earlier headed Oxford in front from Tony Capaldi's corner on his first game back following a four-match suspension.
And Summerfield was delighted with Albion's resilience.
He said: "We showed real character and real grit. Hopefully it's a step in the right direction in terms of our away performances."
The draw took the Brewers into the automatic promotion places for the first time this season.
Conditions at the Kassam Stadium, where rugby side London Welsh also play, were atrocious, with the pitch totally churned up along one side.
Summerfield said: "Conditions were terrible and made it difficult for both sets of players.
"The pitch was in a hell of a state and the wind was swirling badly. Decision-making on the ball was nigh-on impossible.
"To be fair, we did enough to get a result, I felt. We have been trying everything and trying to think of everything, to stop this bad away run. We went back to 4-4-2 and we tried to play."