Watford had to defend for much of the second half but were unlucky not to go ahead through Lee Williamson, who was denied by the woodwork eight minutes from time.
The first half was particularly poor, although Watford went close to scoring when Tamas Priskin headed wide after Williamson had flicked on Jobi McAnuff's corner.
Former Watford striker Heidar Helguson missed QPR's best chance of the first period by heading wide from Lee Cook's free-kick.
It was turgid stuff and prompted Rangers boss Paulo Sousa to make a change at the break, replacing Cook with striker Dexter Blackstock.
The switch initially made some difference and Watford had to withstand a brief spell of Rangers pressure, with Hornets keeper Scott Loach keeping out an acrobatic effort by Patrick Agyemang.
And on 70 minutes, Martin Rowlands' free-kick was headed back into the danger area by Helguson and an unmarked Blackstock was unable rise high enough to add the finishing touch.
Rangers had appeals for a penalty waved away after Agyemang went down in the area under a challenge from Lloyd Doyley as the home side at last began to find some momentum.
They almost went ahead when a goalmouth scramble ended with Helguson's close-range shot being pushed away by Loach and from the resulting corner by Rowlands, Blackstock headed over.
But it was Watford who came closest to breaking the deadlock when Williamson's free-kick from the edge of the area beat keeper Radek Cerny and struck the post.