Brendan Morrison and Sami Salo also scored for the Canucks, who moved four points ahead of Calgary for the Northwest Division lead with their fourth straight win.
Shane Doan had a goal and an assist to extend a seven-game point streak and Jeff Taffe also scored for the Coyotes, who have lost 11 of their past 13.
Cowan gave Vancouver a 1-0 lead early in the first, checking Steven Reinprecht off the puck to start an offensive rush before getting the puck back from Morrison near the crease and beating Curtis Joseph with a short wrist shot.
Morrison made it 2-0 just 96 seconds later when he redirected Brent Sopel’s shot from the point past Joseph.
Naslund extended the lead to 3-0 on a wrist shot over Joseph’s blocker at 12:33 of the first.
Vancouver continued rolling in the second, with Salo sending a shot past Joseph from the left circle as the goalie was screened in front by Vancouver’s Alex Burrows to put the Canucks ahead 4-0.
Doan cut the lead to 4-1 at 11:38 of the period while both teams were skating four-on-four, bouncing a shot off Dany Sabourin’s right pad for his team-leading 24th goal.
Taffe made it 4-2 with 15:28 left in the third period when his shot from the right side of the crease rebounded off the left post and behind Sabourin.
Notes: Cowan had been goal-less on the season until starting his recent run. … The Canucks were awarded a penalty shot midway through the first after a Coyotes player covered the puck with his glove in the crease, but Joseph stopped Henrik Sedin’s attempt with a kick save. … Following the Coyotes’ flurry of moves at the trade deadline, Doan is one of only three remaining Coyotes players with double-digit goals. … Sabourin was making his second start in 2007 and his first since February 20. … The game was preceded by a real-estate seminar, “Foreclosures on Ice.” All participants in the seminar received a ticket to the game.