Justin Schultz responded for the Oilers (3-7-1) who saw a two-game winning streak snapped and have now lost six of their last eight.
The Capitals came close to starting the scoring seven minutes into the first period as Ovechkin tipped a shot that trickled past Oilers goalie Devan Dubnyk and was rolling into the net before he dove back and covered up the puck.
Ovechkin wasn't about to be stopped a second time, however, as he scored his league-leading 10th goal of the season in 10 games with just under two minutes left in the opening period. A face-off deep in Oilers territory came back to the Washington captain and he deposited a quick wrist shot up high past Dubnyk.
Edmonton had a glorious chance to tie the game midway through the second period as a hard rebound came out to Jordan Eberle in front but he shot it wide of the empty net with Caps goalie Braden Holtby trying to get back into position.
Washington went up 2-0 with four-and-a-half minutes to play in the middle period as Ward stood in the paint in front of the Oilers net to screen Dubnyk and was able to direct in a John Carlson point shot.
Edmonton out-shot the Capitals 22-18 through 40 minutes.
Washington extended its lead to three goals just over a minute into the third on a nice tic-tac-toe passing play with Marcus Johansson making a nice pass through the crease to Backstrom, who scored his second of the season and 11th point.
The Capitals made it 4-0 with seven minutes remaining as a turnover allowed a two-on-one and Chimera, who was originally credited with Ward's earlier goal, picked the corner on a snap shot.
The Oilers head right back out on the road for a two-game trip, starting Saturday afternoon in Phoenix. The Capitals play the third game of their five-game trip in Calgary on Saturday.
Notes: It was the second of two meetings between the teams, having already faced each other on Oct. 14 in Washington, where the Capitals won 4-2. It was Washington's first visit to Rexall Place in Edmonton in nearly two years since the Oilers won 2-1 on Oct. 27, 2011… Washington came into the game having lost eight of its past nine in Edmonton... Capitals defenceman Mike Green was back to taking regular shifts after being benched midway through the third period of his team's last game in Winnipeg. It was the first game all season he failed to log at least 20 minutes of ice time… The Capitals are a relatively healthy team, their biggest absence being defenceman Jack Hillen, who is recovering from leg surgery. Conversely, the Oilers are pretty beat up, missing star forward Taylor Hall, who is expected to be out for a month with a knee injury. Also out of the lineup are forwards Sam Gagner (broken jaw), Jesse Joensuu (back), Ryan Smyth (groin), Ryan Hamilton (knee) and Steve MacIntyre (knee).