Barnsley's victory, their first ever win at Wembley, was their season in microcosm.
The Tykes were 23rd in League One in November but a wonderful upturn in form since then has lifted them up to seventh, four points from a play-off spot.
Previous boss Lee Johnson, who left Oakwell for Bristol City shortly after Barnsley had secured their spot in the final, was a guest of the club at Wembley and watched caretaker manager Paul Heckingbottom demonstrate his credentials to take the role on a more permanent basis.
Barnsley trailed to a Callum O'Dowda header in the first half but recovered to lead 3-1. A late goal from Oxford wasn't enough.
Oxford United head coach Michael Appleton told BBC Radio Oxford: "We got off to a good start and got our noses in front, but that second goal did for us really.
"That's something we've tried to avoid this season - conceding too many close together and a strong 20 minute spell for them in the game has done for us.
"We went up a gear once we got a second goal, but we fell a bit short today sadly."