Washington advanced further toward the top of the Eastern Conference standings by winning its sixth in a row, moving within two points of the conference-leading Philadelphia Flyers, who were idle Wednesday.
Holtby was called off the bench last Monday when regular goaltender Michal Neuvirth suffered an injury against Tampa Bay. He wound up making 21 saves over the final two periods against the Lightning and then stopped all three shootout attempts.
Alex Ovechkin and Eric Fehr both scored twice, each producing a goal in the second and third period. Alexander Semin added a tally with 5:30 to go in the third.
Ovechkin has reached 27 goals for the season, 23 short of his total from last year and 38 shy of his career best established in 2007-08.
All five goals came against Nikolai Khabibulin in 36 shots.