Buck pitched for the Beavers from 2004 to 2006, including pitching games in the 2006 College World Series. In 2005, he was an All-American along with Oregon State teammate, outfielder Jacoby Ellsbury. In 2004 and 2005, he played collegiate summer baseball for the Falmouth Commodores of the Cape Cod Baseball League, and won West Division MVP at the league's 2004 all-star game. He had a key part in the 2006 championship series between Oregon State and the North Carolina Tar Heels. Buck won game three of the series after pitching just two days before in game one, sealing Oregon State's first baseball national championship.