The Spartans are hoping Smith can rebuild a program that crumbled with Mel Tucker in charge.
Tucker was suspended in early September and fired later in the month for acknowledging he had phone sex with a vendor who was paid to speak with his team about how to prevent sexual abuse and misbehavior.
Interim coach Harlon Barnett was 2-8 in place of Tucker.
The 44-year-old Smith was 34-35 over six seasons at Oregon State, including an 8-4 mark this year that helped the program earn at least eight wins in consecutive seasons for the first time in more than a decade.
As a quarterback, the Pasadena, California, native led the Beavers to the 2001 Fiesta Bowl. Smith returned as head coach in late 2017, inheriting a team that was 1-11. Previously, he was Washington's quarterbacks coach and offensive coordinator.
Smith had six years remaining on his contract, worth $31.2 million through 2029, with a $3 million buyout.
He faces another big challenge, taking over a team that was routed in each of its four games against highly ranked opponents and with the Big Ten expanding next season to add some powerful programs.
The Spartans lost 41-7 to Washington, 49-0 to Michigan, 38-3 to Wisconsin and closed a miserable season with a 42-0 setback to Penn State.
Michigan State, though, has proven it can compete in college football.
Tucker won 11 games, including a New Year's Six bowl, in 2021 when the Spartans were ranked as high as No. 3 in the College Football Playoff rankings and No. 5 in the AP Top 25.
Mark Dantonio won 36 games and two Big Ten titles in a three-year run that started a decade ago. Nick Saban turned the Spartans into a winner in 1999 before leaving for LSU.
Smith, meanwhile, is leaving a football program with an uncertain future.
Oregon State and Washington State are the lone remaining teams in the Pac-12 after the other 10 teams bolted in realignment. Together the Beavers and Cougars have filed a lawsuit to retain the conference’s assets.
Smith has experience taking over a team in turmoil.
He was hired after the 2017 season in which Gary Andersen abruptly parted ways with the school after a 1-5 start and with seven wins in 2 1/2 years. Interim coach Cory Hall was winless in six games that year.
The Smith-led Beavers won a total of nine games in his first three years before going 7-6 in 2021. He won 10 games last year and shared Pac-12 Coach of the Year honors.
Smith closed his coaching career at Oregon State with a 31-7 loss to rival and sixth-ranked Oregon.
AP College Football Writer Ralph D. Russo and AP Sports Writer Anne M. Peterson contributed.
Follow Larry Lage at https://twitter.com/LarryLage.
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