The visitors managed just one on-target attempt in a game devoid of good goal-scoring chances - the best falling to the Hornets early in the second half when Diego Fabbrini forced Rob Green into a smart save.
The draw means Giuseppe Sannino remains unbeaten after three games as Watford's head coach with his side conceding just one goal in that time.
Rangers came into the match with Charlie Austin still sidelined through injury, so Harry Redknapp chose to deploy Niko Kranjcar as the focal point of the attack.
The Croatian sent a couple of wayward attempts wide in an opening 20 minutes largely devoid of goalmouth action, while Lewis McGugan hit one free-kick against the wall and sent another wide for the home side.
Kranjcar was to go closer with two further attempts before the half-hour mark, both of which went narrowly wide of Manuel Almunia's left-hand post.
But the Hornets also came more into the game as an attacking presence, with Troy Deeney improvising to chest a bouncing Marco Cassetti cross from the right towards goal and Green was also pressed into action to deal with a deflected Sean Murray shot.
Matt Phillips also dragged a shot wide as a relatively low key first period which Rangers shaded ended goalless.
Almunia was the first keeper to be seriously tested five minutes after the restart when he pushed a stinging Phillips drive behind by a corner.
But two minutes later Watford had the clearest opening of the game when Fabbrini played a one-two with Troy Deeney but he was unable to beat Green with his attempted angled finish from eight yards.
Watford began to offer more going forward after that opportunity but they were unable to create another attempt on goal.
By contrast, the visitors' lack of an attacking presence was becoming more evident and Redknapp moved to remedy that in the 70th minute by bringing on Andrew Johnson for Tom Carroll.
Gary O'Neil also came on for the visitors while Sannino refreshed his forward options by bringing on Javier Acuna for Fabbrini but both sides were still struggling to create a clear opportunity.
Murray tried to change that with around 10 minutes remaining by trying two long-range strikes in quick succession - the first was blocked before his next right-footed effort from around 25 yards was safely held by Green.
It looked like the clear-cut chance both teams craved might fall to Johnson when a Phillips cross from the right found him completely unmarked in the area but the flag was already up for offside when he headed wide.