The quality of the home side's attacking play was again a feature of a third straight win for Adrian Boothroyd's men and it resulted in goals for Matthew Spring , Antony McNamee and a tenth of the season for highly rated 20-year-old Ashley Young.
All Rangers had to show for their limited efforts was an injury time consolation from Dan Shittu.
The Hornets were on the front foot from the off and it was only a fine save from Simon Royce which prevented them taking an early lead, the keeper diving away to his left to tip over McNamee's right-footed curling shot.
Marlon King did have the ball in the net soon after but that was ruled out for offside, but Watford continued to boss affairs and Royce again did well to deny King before the home side made the inevitable breakthrough.
A Paul Devlin cross from the right fell for McNamee on the left side of the Rangers area and his return ball to the far post was headed down by Young and Spring bravely flung himself forward to head home from close range.
An excellent James Chambers run nearly resulted in a second for Watford, but they never looked in any real danger until a Stefan Moore pass split the defence and Dean Sturridge raced through, but saw his shot superbly deflected over by Ben Foster.
But that was as good as it got for the visitors until Shittu's late consolation as Watford effectively sewed up the points with 20 minutes remaining.
A throw-in from the right was shielded by King in the Rangers area before he worked the ball back to Spring and the Hornets midfielder rolled the ball to his left, where McNmee latched on to it before calmly beating Royce at his near post.
Watford were fully deserving of their lead and added a third soon after when Young whipped in a free-kick and King dived forward but failed to make contact, but there was still enough pace on the ball to beat the helpless Royce.