"We won the SEC championship," receiver Sammie Coates said. "What else do you want us to do'"
Added Mason: "We feel like we beat the best teams. ... We feel like we deserve to be in the [title] game."
Missouri (11-2) should be in the mix for a New Year's Day bowl, with the Capital One, Cotton and Outback games among the possible destinations.
"We're playing our best football right now," said Auburn Coach Gus Malzahn, making his pitch for a trip to the Bowl Championship Series title game in Pasadena. "I don't know if any other team can say that."
Auburn is certainly playing its best offensively. The Tigers set an SEC championship record with 677 yards, including 545 rushing.
Mason had scoring runs of seven, three and one yards before bursting up the middle on a 13-yard touchdown run that clinched the victory with 4 minutes 22 seconds remaining. He carried the ball 46 times and was selected most valuable player of the game.
"You're looking at one of the top running backs in college football," Malzahn said. "He was a warrior today. Unbelievable."
Auburn, which was 3-9 last season and didn't win a game in the SEC, claimed the title in its first year under Malzahn. Auburn didn't even need a dramatic finish to do it, holding Missouri scoreless in the final quarter.
Missouri also had an impressive season after struggling in its first year in the SEC. But Coach Gary Pinkel's team was denied a quick championship in its new league after leaving the Big 12 Conference.
"There's a real frustration that comes over you on defense when they're coming after you over and over and over again," Pinkel said. "We had trouble stopping it, obviously, and couldn't get it fixed."
James Franklin passed for 303 yards and three touchdowns, and Dorial Green-Beckham caught six passes for 144 yards and a two touchdowns. Missouri piled up 534 yards — the teams combined for 1,211 yards — but it wasn't nearly enough against Auburn's hurry-up spread.
Coming into the game, Missouri was one of the top teams in the nation against the run and ranked second in the SEC behind Alabama. The most yards they had given up on the ground was 184 the previous week in a victory over Texas A&M.
Mason had more yards than that in the first half, putting up 195 by the time he trotted to the locker room and only six yards off the SEC championship-game record. He surpassed the record, set by Louisiana State's Justin Vincent in 2003, on the second play of the second half.
"I've never had holes that big to run through," Mason said. "No one expected 300 yards. I didn't expect it."
Quarterback Nick Marshall shook off two early fumbles, one of which Missouri returned for a touchdown. He ran for 101 yards and a touchdown and passed for 132 yards and a touchdown.
The lead changed hands seven times. Missouri's last gasp was Franklin's five-yard touchdown run, followed by a two-point conversion, that closed the gap to 45-42 heading to the final period.