In 74 games with the Canadiens this season, Beaulieu registered four goals and 24 assists for 28 points and 44 penalty minutes.
The Canadiens will receive Buffalo's third-round pick (68th overall) in the 2017 National Hockey League draft.
Before that Nate split time between Montreal and Hamilton (the Habs old AHL affiliate) from 2012-13 to 2014-15.
Congressman: Ex-aide shows 'feistiness' after shooting
Three Michigan congressman, including Bishop, were all present at the baseball practice when the shooting erupted. He was taken to a local hospital and is now listed in critical condition following surgery.
Last season, the defenceman struggled. He opened the regular season on Montreal's top pairing with Shea Weber. The nail in the coffin was Beaulieu being a healthy scratch during Game 6 of the first round of the postseason against the New York Rangers. The Canadiens were eliminated from the playoffs in that game, losing 3-1.
On Sunday at 10:30am, the National Hockey League announced which players each team had chosen to protect from the upcoming expansion draft.
Beaulieu immediately improves the Sabres' blue line under new coach Phil Housley, a Hall of Fame defenseman.