In 225 career regular-season games, Beaulieu has 60 points (7-53) and 152 penalty minutes.
He was originally drafted 17th overall by the Habs in the 2011 NHL Entry Draft.
Following this trade, the Sabres have seven picks in the 2017 National Hockey League draft.
Last season, the defenceman struggled. Beaulieu started last season as Shea Weber's partner on Montreal's top pairing, but that experiment didn't last long. "After just a handful of games, [then head coach] Michel Therrien decided he had seen enough". In 17 career playoff games, Beaulieu posted four assists.
"Obviously, it's disappointing", Beaulieu said of being a healthy scratch against NY, per the Montreal Gazette.
On Sunday at 10:30am, the National Hockey League announced which players each team had chosen to protect from the upcoming expansion draft.
While the Canadiens weren't expected to protect the 2011 first-round pick, Buffalo did at the expense of exposing two more high-profile and higher-priced defensemen in Zach Bogosian and Josh Gorges.
It'll be from the penthouse to the basement for Beaulieu, who departs the 47-26-9 Canadiens for the 33-37-12 Sabres.