John Marquis and Koby Arthur scored the goals to take Cheltenham through to the second round of the Johnstone's Paint Trophy as the Robins defeated Oxford 2-0 at Whaddon Road.
And a miserable night for the visitors, who are still looking for their first win of the season, was compounded by having defender Jon Meades sent off midway through the second half.
There were early chances for both sides with Craig Braham-Barrett finding the Oxford crossbar with a ninth-minute cross and Joe Riley forcing Cheltenham goalkeeper Trevor Carson into a good save five minutes later.
In the 20th minute Marquis headed over after getting on the end of another fine Braham-Barrett cross, and then Danny Hylton missed the target at the other end from a corner.
The breakthrough came in first-half injury time when Joe Hanks' corner found Marquis who neatly directed the ball into the roof of the net from six yards out.
Meades saw red after 68 minutes for his high challenge on Jason Taylor, with the Robins midfielder picking up a yellow card for his retaliation.
And the home side made sure of victory when substitute Terry Gornell crossed for Arthur who headed his fourth goal of the season.