Miller, who won't turn 20 until March, gave the Rangers a 1-0 lead just 1:29 in and then pushed their advantage to 3-1 in the second period with a rare power-play goal for the club. Marian Gaborik also scored, defenceman Marc Staal had two assists and Ryan McDonagh added an empty-net goal to give the Rangers their second win in three games.
New York lost in Miller's NHL debut Tuesday at New Jersey.
The Rangers have an eight-game winning streak over the Islanders at Madison Square Garden, outscoring them 35-11.
It was a different game in the past, that's for sure. It's not exactly what I was expecting but I think the experience paid off for a lot of our guys that realized what it takes in a Game 7. Realistically the effort we put forward, we might not even had to put 60 [minutes], but we just couldn't get a couple bounces to go our way and we just kept pushing.
— Capitals goaltender Braden Holtby on Washington's play in Game 7 vs. the Islanders