AUSTIN, Texas — Bye-bye Big 12, hello SEC. Texas and Oklahoma made their long-awaited conference switch with campus parties, carnivals, concerts and fireworks.

The three-years-in-the-making switch to the Southeastern Conference for two programs that were co-founders of the Big 12 in 1996 became official Monday.

And for their move to a league where “It Just Means More,” Texas and Oklahoma hosted colorful celebrations Sunday and Monday.

At Texas, thousands poured onto campus in near 100-degree heat Sunday for a carnival and concert under the iconic campus clock tower.

Oklahoma’s festivities started Sunday night and stretched to events statewide on Monday.

The SEC Network had live programming from both campuses over the two days.

“We’ve had the mantra it just means more since 2016,” said SEC Commissioner Greg Sankey, who visited both campus parties, “Oklahoma and Texas fit that clearly.”

Texas women’s head basketball coach Vic Schaefer, who coached in the SEC, called the switch “a match made in heaven.”

At the Texas party, children played on bounce houses, rock walls and slides. Misters cooled their parents who waited in long lines for autographs from Longhorns coaches, photographs with Longhorns mascot Bevo, and packed into merchandise tents.

“This is a day we have been building toward for years,” Texas Athletic Director Chris Del Conte said. “Our fans our really excited about this. You can tell by the turnout.”

It’s a moment college sports in general has been building toward in the era of major realignment. The Texas and Oklahoma break from the Big 12 helped trigger myriad conference shifts with more on the way. By the first kickoff of the 2024 season, 11 so-called Power Four programs will be in new conferences.

The Big Ten will grow from 14 to 18 teams with Southern Cal, UCLA, Oregon and Washington poached from the Pac-12. The beleaguered West Coast league also lost Arizona, Colorado, Utah and Arizona State to the Big 12, and California and Stanford to the Atlantic Coast Conference. Southern Methodist leaps from the American Athletic Conference to the Atlantic Coast Conference on Monday.

As for Oklahoma and Texas, they originally planned to join the SEC in 2025, but ultimately reached a financial deal with the Big 12 for an early exit. And they leave with a whole lot of hardware.

Between them, the Sooners (14) and Longhorns (four) won 18 Big 12 football titles in 25 years, with Texas winning the crown last season for the first time since 2009.

In its final year in the league, Texas won 15 league regular season or tournament championships across all sports, and national titles in volleyball and rowing. Oklahoma capped its final season with its dominant softball program winning its fourth consecutive national title in May. The Sooners beat Texas in the final.

“Texas brings more tradition, more talent, more passion and more fight,” to the SEC, the school said on its athletics website.

All that winning will be much more difficult to duplicate in the SEC. Oklahoma opens its first SEC football schedule at home against Tennessee on Sept. 21. The Longhorns debut at Mississippi State on Sept. 28.

Since the start of the College Football Playoff in 2014, SEC schools have won the championship six times.

Texas (2005) and Oklahoma (2000) were the two schools to win national titles in football while in the Big 12.

Some traditional rivalries will be stitched back together, and some torn apart.

The Texas-Texas A&M rivalry is reborn. It had been on hiatus since A&M left the Big 12 for the SEC in 2012. Oklahoma’s Bedlam rivalry with Oklahoma State is ruptured.

Texas spiced things up with Texas A&M last week when it poached Aggies head baseball coach Jim Schlossnagle to Austin. At his introductory news conference, Schlossnagle warned Longhorns fans that the SEC is the “major leagues” of college baseball. The league has won the last five national championships.

Oklahoma’s celebration started Sunday night with a 5k race through the heart of campus and fireworks.

On Monday morning, former Sooners head football coach Barry Switzer co-hosted a celebration breakfast in Tulsa. Later in the day, Oklahoma planned a campus party at the football stadium with live music and entertainment.

“We couldn’t be more excited to join the SEC. Our teams are poised for success and look forward to the competition with many of America’s most outstanding universities,” Oklahoma Athletic Director Joe Castiglione said.