The moves by new general manager Reggie McKenzie were the latest to bolster the line and secondary as he has added only to those two positions so far this offseason.
After spending most of his first two years with the Raiders as a reserve, Barnes started all 16 games at right tackle last year before becoming a free agent. He ended up staying in Oakland after reaching a deal that could be worth up to $2 million, said his agent, Kenneth Zuckerman.
While Bartell and Spencer have extensive starting experience in the NFL, Lee has started just one game since being picked in the second round by the Packers in 2008 out of Auburn.
Lee was almost exclusively a special teams player last season. He had just one defensive tackle and was targeted just once all season in pass coverage.