An outside linebacker, Thompson, 27, likely signed for the veteran's minimum of $540,000. Barry and O'Sullivan signed their tender offers of $656,000.
Thompson, a 6-foot-3, 229-pounder, spent his first five seasons with the Cardinals, where he recorded 443 tackles, 6 1/2 sacks, two forced fumbles and one fumble recovery in 65 games. Thompson started 21 games over his first two seasons after getting selected in the second round (41st overall) by the Cardinals in the 2000 NFL Draft. In 2002, he started all 16 games and finished with 139 tackles (81 solo) and 2½ sacks.
Thompson suffered a training-camp injury early last season and played in 11 games, recording 42 tackles and one sack.
The Packers are taking a chance on Thompson, who has two strikes against him in the league's substance abuse program, according to a report in the Milwaukee Journal-Sentinel. He was suspended for four games in 2003 for violating the policy. If Thompson violates again, he will be suspended for one year.
Barry, a 6-foot-4, 335-pound native of Racine, played in 13 regular season games last year, including three starts as an extra tight end in the Packers' U-71 package. He originally joined the Packers as a non-drafted free agent before the 2002 season.
In three NFL seasons, Barry has played in 43 games with seven starts.
O'Sullivan, a 6-foot-2, 220-pound quarterback from the University of California-Davis, spent most of the 2004 season as the Packers' No. 3 signal-caller. Acquired Oct. 4 with the Saints' second-round choice in today's NFL Draft, O'Sullivan replaced an injured Doug Pederson. Green Bay sent New Orleans CB Mike McKenzie and a conditional '06 draft choice in the trade. O'Sullivan, the 15th backup quarterback on a Packers 53-man roster during Brett Favre's current streak, made his NFL debut Jan. 2 at Chicago, taking the final two snaps.