"We didn't have any expectations when we came here and just wanted to adjust to the new surroundings," Stuart said. "But the last couple of weeks we have settled in on the ice and in the dressing room and our teammates are finding out what we bring as well."
"A lot of people in the East don't know those guys because they have been in the West their whole career," Primeau said. "They bring a lot to the table and they're a big reason for our success so far."
The Bruins won their third straight and reached the .500 mark for the first time since Nov. 12.
"It takes time for players to become part of the team," Bruins general manager Mike O'Connell said. "When you lose your captain and three new players come in, everybody has to redefine their roles."
Alexander Ovechkin missed a chance to tie the game for Washington when he failed to convert a shorthanded breakaway with 3:20 to play.
Ovechkin was also awarded his first career penalty shot after he was tripped on a breakaway by Nick Boynton, but was stymied by Thomas at the 2:50 mark of the second period.
"It's my fault we lost the game," Ovechkin said. "I must take advantage of those chances, but it was not my day."
Tim Thomas made 31 saves and is 5-0-2 since taking over as starting goalie for the Bruins.
Eric Nickulas gave Boston a 2-1 lead when he took a perfect feed from Primeau and slid the puck past Johnson with 40 seconds left in the second period.
Brad Boyes' power-play goal gave the Bruins a 1-0 lead when he backhanded a rebound of a Stuart shot past Johnson 2:36 into the first period. Boyes has seven points in the last five games.
Halpern had two assists for the Capitals, who have lost three straight.
Patrice Bergeron had two assists for the Bruins, who have beaten Washington in all three meetings this season.Game notes
Primeau and Stuart each had an assist. ... Ovechkin is the only player in the NHL with twice as many goals, assists and shots as any teammate. ... Stuart played in his 400th NHL game for Boston. ... The Bruins are 9-1-1 against the Southeast Division. ... Boston is unbeaten in its last six games and has won more games in January than any other month this season with a total of seven.