CHICAGO -- The Chicago Bears added to their backfield and defensive line, agreeing to a two-year contract with running back Marion Barber and a one-year deal with nose tackle Amobi Okoye on Saturday.

The also re-signed cornerback and special teams contributor Corey Graham to a one-year deal.

Barber spent the last six seasons with the Dallas Cowboys, running for 4,358 yards and 47 touchdowns -- sixth in the NFL during that span. He added 1,280 yards receiving.

He was officially released by the Cowboys this week along with former Pro Bowl receiver Roy Williams, who joined the Bears on Friday.

Okoye wasn't out of work for long, either, after being cut by Houston on Saturday.

The youngest first-round draft pick in NFL history when he was taken 10th overall in 2007 at age 19, he had a career-high 44 tackles in 2010, including three sacks. But the Texans' defense ranked among the league's worst in most categories. Houston used six of its eight draft picks on defensive players, and new defensive coordinator Wade Phillips plans to use Shaun Cody and Earl Mitchell at nose tackle, leaving Okoye out of the mix.

In four seasons with Houston, he had 138 tackles, 11 sacks, two forced fumbles and two fumble recoveries.

Graham has appeared in 61 games over four seasons with the Bears and has 111 tackles, one interception and nine pass breakups. His 82 special teams stops rank second to Adrian Peterson's 110 on the club's list since the statistic was first recorded in 1995.

Graham led Chicago with 25 special teams tackles last season.

The Bears also waived guard Herman Johnson on Saturday.