Wednesday's start of the Women's College World Series championship closes a chapter of Oklahoma softball, as it does for longtime conference rival and WCWS opponent Texas.

Indeed, it marks the end an era of college athletics as a whole.

The best-of-three series between the No. 1 national seed Longhorns and No. 2 Sooners is the last time the two programs face off head to head, in any sport, as Big 12 Conference opponents. Both Oklahoma and Texas will head to the Southeastern Conference next month.

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Of course, the two longtime Big 12 teams catalyzed the era that college athletics is soon to enter when the new NCAA calendar year begins next month on July 1: conference realignment.

After the Sooners and the Longhorns broke away from the Big 12 — of which they were founding members — the Pac-12 Conference began to dissolve as USC and UCLA made a break for the Big Ten Conference. Oregon and Washington followed the L.A.-based schools to the Big Ten, whereas Arizona, Arizona State, Utah and Colorado then defected to the Big 12. Stanford and Cal later accepted invitations to the ACC.

As such, the Pac-12, one of the most storied conferences in the history of college softball, saw its last head-to-head matchup in the sport in Sunday's WCWS elimination game between UCLA and Stanford. Curiously, Oklahoma and Texas had a hand in creating the final Pac-12 softball game in history: The Longhorns beat Stanford 4-0 in the opening round to send them to the loser's bracket, whereas Oklahoma beat the Bruins 1-0 in the second round to force the elimination game.

Both the Sooners and Longhorns will now look to end their tenure in the Big 12 on a high note, while also creating some softball history: Patty Gasso's squad aims to become the first team in the history of the WCWS to four-peat as national champions, whereas Mike White's Longhorns will look for their first title in program history.

Here's what you need to know on when Oklahoma and Texas join the SEC:

When do Oklahoma, Texas join the SEC?

The Sooners and Longhorns are set to join the SEC officially on July 1, 2024. The schools previously were contractually obligated to remain in the conference through the end of the 2024-25 academic calendar, but were able to leave a full year early at the combined cost of $100 million in revenue.

With that, Wednesday's WCWS championship series serves as the final head-to-head matchup between Oklahoma and Texas in any sport as members of the Big 12 Conference. The Sooners and Longhorns' move from the Big 12 to the SEC has been in the works for quite some time, as both universities' boards of regents "unanimously" accepted the SEC's invitation to join the conference in 2021.

"This is an important moment for the long-term future of the Southeastern Conference and our member universities," SEC Commissioner Greg Sankey said in a statement in 2021 on Oklahoma and Texas accepting the conference's invites. "Oklahoma and Texas are outstanding academic institutions with two strong athletics programs, which will add to the SEC's national prominence."

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What teams are in the SEC?

The Sooners and the Longhorns will be the SEC's first additions since former Big 12 programs Missouri and Texas A&M joined the conference in 2012. Oklahoma and Texas will bring the conference membership to 16 teams.

Here's the full list of SEC teams, with the additions of Oklahoma and Texas, in alphabetical order:

• Alabama

• Auburn

• Arkansas

• Florida

• Georgia

• Kentucky

• LSU

• Mississippi State

• Missouri

• Ole Miss

• Oklahoma

• South Carolina

• Tennessee

• Texas A&M

• Texas

• Vanderbilt

What teams are in the Big 12?

Even with Oklahoma and Texas leaving the Big 12, the conference was able to add several new members. In 2023, it added independent BYU and American Athletic Conference teams in Cincinnati, Houston and UCF. In 2024, it added Pac-12 schools Arizona, Arizona State, Colorado and Utah.

Here are the Big 12's 16 member institutions, in alphabetical order, as of the 2024-25 academic year:

• Arizona

• Arizona State

• Baylor

• BYU

• Cincinnati

• Colorado

• Houston

• Iowa State

• Kansas

• Kansas State

• Oklahoma State

• TCU

• Texas Tech

• UCF

• Utah

• West Virginia

This article originally appeared on Oklahoman: When do Oklahoma, Texas join SEC? WCWS championship is teams' last Big 12 meeting