The 5-foot-11, 185-pound cornerback delivered the good news to defensive coordinator Nick Aliotti, a day after officially receiving his offer.
"I've been talking to Oregon since the season ended, but I got offered yesterday," Harrison said. "It was already in my plans to commit to Oregon because they are one of my top schools."
Harrison was recruited by Aliotti and secondary coach John Neal. He said that the coaches liked his length and athletic ability at the corner position, believing he will be a good fit for their system after a recent evaluation.
"It made me realize how bad they wanted me," Harrison said. "It makes me want to go play for them."
Oregon has always been a top choice for Harrison, having watched them since he was a young child. Last season, Harrison had 15 tackles and four interceptions for Contra Costa, and he's ready to elevate his game in a Ducks uniform.
"It's definitely exciting," Harrison said. "I'm ready to just get out there and showcase my talents."
After graduation in the winter, Harrison will depart for Eugene. He said that Aliotti wants him on campus as soon as possible to start learning the system.
"They want me to come in and make an impact," Harrison said. "They know I can be a playmaker."
Though he committed without taking an official visit, Harrison has family in the area and has been around Oregon several times. He admitted that he wanted to know more about the campus life, but is excited about playing inside of Autzen Stadium. He will have three years to play two after the 2013 season.
"I'm ready to see what that's like," Harrison said. "I'm going to enjoy playing at Autzen. It's going to be an experience knowing that my family is there, watching me. It's going to be a real stepping stone."
When it comes to making an individual impact, Harrison already has set the bar high for himself.
"I want to be an All-American," Harrison said. "I've got to be."