K.J. Costello will announce his college commitment on Thursday, he wrote on Twitter.
The Santa Margarita High quarterback is set to choose among Michigan, Stanford and USC.
At the Opening Regional in Los Angeles, Costello said he began considering Michigan after Coach Jim Harbaugh was hired. "I really do believe that in the next year or so he is going to turn that program around and possibly win a national championship," he said.
Stanford has recruited Costello since his freshman season, he said.
USC is the family favorite.
"It's an hour from home, my grandparents and everybody lives right up there," said Costello, whose mother attended USC. "I've been an 'SC fan my whole life."
Costello, 6 feet 5 and 220 pounds, is considered a top-rated prospect in the 2016 recruiting class.