The Big 12 is in its 30th football season, 20 years after last winning a national championship and now in a much different era of the game than when the conference started.

Like many 30-year-olds, the league has gotten bigger while going through plenty of ups and downs. There have already been some this season.

TCU provided a much better finish to the Big 12’s holiday weekend than how it began. The Horned Frogs won 48-14 at North Carolina to spoil Bill Belichick’s debut in a prime-time Labor Day game highly anticipated because of the 73-year-old coach who won six Super Bowl titles before his first college game.

While most talk nationally will still be about Belichick’s loss, it was a boost for the Big 12 after losses in its first three games this season against teams from other Power Four leagues: Cincinnati at Nebraska, and Colorado (to Georgia Tech) and Baylor (to Auburn) at home.

No. 25 Utah won 43-10 at UCLA 43-10 late Saturday. But Kansas State that same day, a week after a 24-21 loss to Iowa State in Dublin, Ireland, needed a last-minute touchdown to beat FCS team North Dakota.

Five different schools have been Big 12 champions the past five seasons. Arizona State made the new 12-team College Football Playoff last year after being the preseason pick to finish last in its league debut.

All the other power conferences, even the now-rebuilding Pac-12, had multiple champions in that same period. The SEC (Alabama), Big Ten (Michigan) and ACC (Clemson) have all had three-time champs in the 2020s. No. 16 Iowa State, No. 24 Texas Tech, newly ranked Utah and TCU are among the top contenders for the Big 12 title.

So are Arizona State and Baylor, which had won six regular-season games in a row before losing to Auburn. The Bears’ league title in 2021 ended Oklahoma’s record run of six consecutive championships, followed by Kansas State, Texas and the Sun Devils.

The Big 12’s three national championships came from undefeated teams in the conference’s first 10 seasons: Nebraska in 1997, Oklahoma in 2000 and Texas in 2005. All now play in different leagues.

Nebraska left in 2011, part of a tumultuous period in the Big 12’s teen years. The Huskers went to the Big Ten at the same time Colorado left for the Pac-12 in the first changes to the original 12-team configuration that has since had seasons with 10, 14 and now 16 teams.

Texas A&M and Missouri departed for the SEC in 2012, when TCU and West Virginia entered the Big 12. Longtime independent BYU joined with American Athletic Conference teams Houston, Cincinnati and UCF a 14-team setup in 2023, a year before Texas and Oklahoma made their planned move to the SEC while Colorado returned from the dismantling Pac-12 along with Arizona, Arizona State and Utah.

TCU in 2022, its first season with coach Sonny Dykes, was the only Big 12 team to make a national championship game appearance in the 10 seasons of the four-team playoff (2014-23).