Burnley stretched their unbeaten run to five games with a goalless stalemate at Vicarage Road but it was two points dropped for the visitors following a catalogue of missed opportunities.
Another slow start could have been of detriment to the Clarets, just as it had been against Fulham, but Gerard Deulofeu was unable to repeat what Andre Schurrle had done previously.
The Spaniard only had Tom Heaton to beat when Troy Deeney's ball over the top had caught out Burnley's defence but the visiting skipper came out on top.
Despite initial hesitation the 32-year-old stopper, restored to the side last month, made himself big to get a glove to the strike and flick the ball wide of the upright.
When the former Everton forward failed to connect with a header inside the box, misjudging Kiko Femenia's cross, it looked like it could have been a long afternoon for the Clarets.
However, Sean Dyche's side barely gave the hosts a sniff for the remainder of the half. Ben Mee's header wide from Dwight McNeil's corner was the start of a series of attempts at goal.
The centre back was then the man on the end of Ashley Westwood's pinpoint diagonal but, from the far side of the area, Mee failed to find the target.
The away side identified Watford's weakness early on, shaping the ball round the back of Christian Kabasele, and after Chris Wood had got the better of the Belgian international, and played the ball in to the area, it was up to Adrian Mariappa to thwart Ashley Barnes.
The Clarets striker wasn't to be denied an attempt on target moments later, when Westwood's delivery dropped over Kabasele, but the header was blocked by Foster.
McNeil hit the side-netting from a set-piece as Burnley's assault gathered pace before another big opportunity for Barnes to open the scoring went begging.
There wasn't much that needed to be done when Mariappa inadvertently flicked Phil Bardsley's cross in to the forward but, leaning back slightly, he swiped at the ball left-footed and hit the hoardings.
The Hornets almost made their opponents pay in the latter stages of the half as Deulofeu fired wide from outside the penalty area.
And, after Wood turned Mariappa to find the wrong side of the upright, Heaton pulled off a superb reflex save to deny Deeney from sweeping home Femenia's cross.
The away side continued to dominate proceedings after the break and Bardsley's cross in to the six yard box was just out of the reach of Barnes.
Foster then made his presence known to keep out Jeff Hendrick once the midfielder had been picked out by Wood.
It was backs to the wall for Javi Gracia's men at times and they were ever-so-lucky not to fall behind when McNeil had a golden chance to open the scoring.
Westwood's corner was won, once again, by Mee and it seemed the teenager would break the net, not just the deadlock, as the ball fell. But, just yards from goal, he blazed his volley over the bar.
Heaton was untested for much of the second half as Roberto Pereyra's effort dropped wide of the far post while it took a routine save to keep out Tom Cleverley's strike from 20 yards out.
With time running out the away side thought they'd nicked it when Wood followed up after Foster had repelled McNeil's effort.
The linesman's flag was raised, denying the Clarets a late winner and a fourth successive Premier League triumph, though replays showed that the New Zealand international was onside.