''I've been working hard lately, trying to get my game going,'' said Oshie, who hadn't scored since Jan 31, a span of 19 games. ''It felt nice. But more importantly it was good to get a team win with scoring up and down the lineup.''
It was the first time this season the Capitals had scored seven times and their three-game winning streak is their first since early January. They remained tied with Pittsburgh atop the Metropolitan Division, but currently hold the tiebreaker with two games in hand.
Andrei Burakovsky added a goal and an assist, and Lars Eller and John Carlson also scored to help Washington improve to 10-4-3 in its last 17 games against the Islanders. Evgeny Kuznetsov had three assists and Philipp Grubauer finished with 35 saves for his 11th win of the season.
''We capitalized on some opportunities and Gruby was really strong tonight,'' Capitals coach Barry Trotz said. ''And we had little bit of luck.''
Despite the lopsided result, Islanders coach Doug Weight was somehow satisfied with his team's effort.
''We played pretty well. We had some good chances,'' he said. ''The guys kept working and shooting.''
Orlov gave the Capitals a 3-2 lead with 2:43 left in the first as he beat Gibson for his ninth of the season.
Burakovsky extended Washington's lead at 3:12 of the second, and Backstrom made it 5-2 with his 18th with 9:38 remaining in the middle period, ending Gibson's night.
Carlson got his 13th with 4:19 left in the third to give the Capitals a four-goal lead.
Pulock got the Islanders to 6-3 just 52 seconds later, but Oshie scored an empty-netter for his second of the night and 14th of the season with just under two minutes to go.
The Islanders were coming off a 5-2 win at Calgary on Sunday night that snapped their eight-game skid (0-4-4) with Gibson making 50 saves. However, their defensive struggles returned against the Capitals.
The Islanders have allowed a league-high 252 goals and are 15-23-8 since finishing November at 15-7-2. They will almost certainly miss the playoffs for the second straight year and the third time in five years.
New York has won only one playoff series - in 2016 - in the nine-year career of their captain John Tavares, who is set to become an unrestricted free agent in July.
Weight replaced Jack Capuano behind the bench midway through last season and the Islanders surged to finish with 94 points, narrowly missing the postseason.
But their play has been haphazard this season and amid their most recent swoon - especially at home - their season is on the ropes. They are 4-10-1 at Barclays Center starting with a Jan. 2 loss against Boston.
Nelson opened the scoring at 2:19 of the first as he took a pass from rookie Tanner Fritz while skating down the slot before beating Grubauer for his 16th.
Eller tied it at 10:19 with his 16th before Oshie scored at 11:29 to put the Capitals ahead 2-1.
Ladd tied the score 2-2 at 12:29 when he scored his 10th. Rookie Mathew Barzal got his team-leading 52nd assist on the play.
NOTES: Washington is 26-12-5 against Eastern Conference opponents this season. ... The Islanders on Thursday signed forward Scott Eansor to a two-year, two-way contract. The 21-year-old Eansor has 16 goals for AHL Bridgeport this season. He was a teammate of Barzal with the junior Seattle Thunderbirds previously. ... The Islanders scratched D Dennis Seidenberg, D Sebastian Aho and F Chris Wagner. ... Washington scratched D Christian Djoos, F Alex Chiasson and F Travis Boyd.
Capitals: Host the Islanders on Friday.
Islanders: At Washington on Friday.
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