Thompson and Clark both struggled during the team's training camp. Clark was selected in the seventh round of April's NFL draft, and Thompson was signed as an undrafted free agent.
Clark is the first of Green Bay's 11 draft picks to be released. Wide receiver David Clowney was released in the team's final cutdown Sept. 1, but re-signed to the practice squad a day later.
Bell passed for 7,779 yards and 62 touchdowns at West Texas A&M. He guided the team to back-to-back Lone Star Conference Championships the past two seasons and compiled a 20-4 record as a starter.
Bell signed as a non-drafted free agent with the Carolina Panthers in May and was released in the team's final cutdown.
Stephenson was a fifth-round pick of the Pittsburgh Steelers in the 2007 NFL Draft. A two-year letterwinner at Rutgers, Stephenson played on the defensive line as a 2005 junior before switching to offensive line as a senior. He started all 12 games at right guard in 2006 and earned second-team All-Big East accolades.