The 2011-12 season will be the final one of McQuaid's current contract, and he would have become a restricted free agent on July 1, 2012.
"(Boston) is where I want to be," McQuaid told reporters during a conference call announcing the deal. "It's where I want to be for a long time. Being able to get it done, to know that you are going to be where you want to be … I'm obviously very excited."
The departure of Tomas Kaberle to Carolina opens the door for McQuaid to possibly earn an even greater role along the blue line for the Bruins in 2011-12. He entered his first full season with the club in 2010-11 as the club's seventh defenseman.
In 67 games last season, the 24-year-old had 3 goals, 12 assists and a plus-30 rating, which led all rookies and was tied for fifth among all players. He also was third on the team with 131 blocked shots and seventh with 102 hits. In 23 playoff games, McQuaid had 4 assists, was tied for fourth on the team with 32 blocked shots and 30 hits. He went scoreless with a plus-3 rating in seven games against the Vancouver Canucks in the Stanley Cup Final.
"Adam is a real solid contributor with his size, toughness and range," Bruins General Manager Peter Chiarelli said. "We felt fortunate to lock him up. His willingness to learn stood out the most."
In 86 regular-season NHL games, McQuaid has 4 goals and 12 assists.
A native of Charlottetown, PEI, McQuaid was selected by Columbus in the second round of the 2005 Entry Draft, and was acquired by the Bruins on May 16, 2007 in exchange for a fifth round pick in the 2007 draft.
"The trade was one of the best things that ever could happen to me," McQuaid said.
Chiarelli said the next order of business is re-signing restricted free-agent forward Brad Marchand. In 2010-11, his first full NHL season, Marchand had 21 goals and 41 points in 77 regular-season games, and 11 goals and 19 points during Boston's Stanley Cup run.
The Bruins also signed a pair of prospects Thursday. Forward Craig Cunningham, a 2010 fourth-round pick, signed a three-year, entry-level contract. The 5-foot-10, 185-pound right wing had 27 goals and 60 assists in 77 games in the Western Hockey League with the Portland Winterhawks and the Vancouver Giants last season.
The team also signed defenseman Zach McKelvie to a one-year contract. Per team policy, terms of those deals were not disclosed. McKelvie had signed with the Bruins in 2009, but obligations to the U.S. Army -- he played four years at the school -- prevented him from joining the team. A 6-2, 200-pound defenseman, McKelvie had 14 goals and 44 assists in 134 NCAA games.