Oates is expected to be in uniform today when the Bruins play the New Jersey Devils in Boston. He is the league's seventh-leading scorer this season with 59 assists and 10 goals.
"He is multidimensional, and we feel he can get the puck to any wing at any time," Bruins assistant general manager Mike Milbury said of Oates, 29, who scored more than 100 points in the previous two seasons, including 115 last season with 25 goals and 90 assists.
"We think he will be another 100-point player for us, and we feel this deal brings us closer to where we want to be," Milbury said.
Oates said he hadn't wanted to be traded, but that it was probably the best thing for the Blues.
"I guess I'm glad it's finally over," Oates said. "I obviously didn't want to leave. I never thought it would get to this point."
The move ended a dispute between Oates and Blues management over the club's refusal to renegotiate his contract for a third time.
Blues coach Brian Sutter said he was glad the matter was resolved.
"It became more and more obvious that things were not going to work out for him here," Sutter said. "It's been worrying the team since the first of the year. It affects the players. I wish him well and hope he can put up the same kind of numbers for Boston. Now we can get down to playing hockey."
The Blues (23-22-9) are in third place in the Norris Division, 11 points behind the Detroit Red Wings.
Janney, 24, in his fourth season with the Bruins, has 12 goals and 39 assists in 53 games. Quintal, 23, has four goals and 10 assists in 49 games. After learning about the trade, Janney said he "went down and slugged a cold beer and try and get the composure."
"We have acquired an excellent two-way playmaker in Janney, who can play on the power play and kill penalties," said Ron Caron, Blues vice president and general manager.
Lemieux, who met with NHL president John Ziegler, said referee Ron Hoggarth "just can't keep up with us. . . . He's so bad. . . . It's a disgrace to this game. As long as we have people like that, the game's not going to go anywhere."
Ziegler said those remarks could not be tolerated.
"He indicated these remarks grew out of a series of frustrations," Ziegler said. "Despite provocation, public remarks critical of NHL officials . . . must be penalized."