Brady and nearly the entire team participated in the first of four days of this week's organized team activities, Patriots spokesman Stacey James said.
The first three days of OTAs were held last week for young players and others signed as free agents in the offseason who needed more time to get used to the playbook. About 50 players, roughly half the team, took part in those. The sessions are voluntary.
The only media access for this week's sessions is Thursday. James said Tuesday that Brady threw passes and did other activities during his first formal practice with the club since he suffered a torn left knee ligament midway through the first quarter of the Patriots 17-10 win over the Kansas City Chiefs.
The Patriots plan a total of 12 OTA days, two fewer than the maximum allowed by the NFL. Players do not wear full pads.
Brady had surgery Oct. 6 and a subsequent operation for an infection in the knee.
There have been numerous signs that the NFL MVP in 2007 would be ready for the season opener Sept. 14 against the Buffalo Bills.
In an interview for this week's issue of Sports Illustrated, Brady said he has no pain or restrictions in his movement when he runs and cuts.
He was quoted as saying that he is "as confident as anyone could be that I'll be ready to play, back to playing normally, when the season starts. I've done everything I could to push myself, sometimes too hard. Right now, I'm doing everything. Literally everything. There's nothing I can't do."
The article also quoted the 31-year-old Brady as saying, "I want to play until I am 41."
On Feb. 18, Brady, a two-time Super Bowl MVP, said his recovery was on schedule for him to be ready for the opener.
Ten days later, the Patriots traded Matt Cassel, who had replaced Brady, to Kansas City. Cassel hadn't started the previous seven seasons with Southern California and the Patriots but led New England to an 11-5 record but no playoff berth. He started all 15 games after taking over for Brady in the opener.
The Patriots did not add a veteran quarterback in the offseason, leaving 2008 third-round draft pick Kevin O'Connell as Brady's primary backup
Brady, who has thrown passes to receivers during the offseason, was upbeat in an interview last week with "Patriots Today," the team's in-house Internet show.
"I'm feeling great and just excited to be out there on the field, training with my teammates," Brady said. "It's always fun being back in this competitive environment and working with these guys to try to make 2009 our best season. It's been fun to be back."