Alex Ovechkin was the stand-out performer for Washington with two goals and two assists, including setting up Green in OT, with Troy Bouwer also on the scoresheet.
Cody Hodgson scored twice for Buffalo, who also had goals from Christian Ehrhoff and rookie Phil Varone.
James van Riemsdyk scored a late winner as the Toronto Maple Leafs edged out the Tampa Bay Lightning 3-2.
Nazem Kadri had scored twice to put the Leafs 2-0 up before Matthew Carle and Mark Barberio led the fightback for Tampa Bay.
Milan Lucic scored twice to lead the Boston Bruins to a 6-2 win over the Florida Panthers.
Zdeno Chara, Reilly Smith, Shawn Thornton and David Krejci were also on the scoresheet for the Bruins, who got their third straight six-goal win.
Scott Hartnell had two goals and an assist and Steve Mason claimed his second shut-out of the season on 33 saves to lift the Philadelphia Flyers to a 5-0 rout of the Detroit Red Wings.
Oliver Ekman-Larsson scored twice and Thomas Greiss made 30 saves for the shut-out as the Phoenix Coyotes eased past the Los Angeles Kings 3-0, while Jaroslav Halak blanked New Jersey as the St Louis Blues beat the Devils by the same scoreline.
The Ottawa Senators edged out the Columbus Blue Jackets 3-2, the Montreal Canadiens were 3-0 winners over the Carolina Hurricanes and the Nashville Predators overcame the Winnipeg Jets 4-3.
There were also wins for the Calgary Flames and the Minnesota Wild.