The Raiders waived WR Montay Crockett in a corresponding move. Financial terms of the contract were not immediately announced.
Injuries have plagued Cooper's career. He missed all of his rookie year with a broken leg and finished last season on injured reserve with a biceps injury.
Cooper has played only 22 games the last three years. Richie Incognito, who is expected to start at left guard, is suspended for the season's first two games after violating the league's personal conduct policy.
Cooper started a school-record 48 games for North Carolina at left guard and was a three-time All-ACC selection in college.