CHRIS Brunt's last-gasp header five minutes into stoppage time salvaged a precious point for Albion in a battling draw at Vicarage Road.
But the Baggies will have to put the Champagne on ice as they cannot now mathematically clinch automatic promotion until Saturday at the earliest.
Ten-man Watford looked like making it a massive anti-climax for Roberto Di Matteo's men when Danny Graham's 85th-minute thunderbolt found the back of the net.
The relegation-threatened hosts showed great resilience even after Jon Harley was sent-off for a second bookable offence ten minutes from time.
But they could not hang on as Brunt repeated his Portman Road rescue act from earlier in the season with another dramatic late equaliser to extend the second-placed Baggies' unbeaten run to eight games.
Giles Barnes was handed his first Albion start as he came in for the benched James Morrison and lined up on the right wing, with Robert Koren moving into the centre.
Gianni Zuiverloon replaced the injured Steven Reid (hamstring) at right-back and Roman Bednar was restored in attack as Ishmael Miller dropped to substitute.
The Hornets were without Henri Lansbury, Heidar Helguson and Martin Taylor, with Don Cowie, Danny Graham and Lee Hodson replacing them in the hosts' starting XI.
Watford gave the Baggies an early scare in the third minute when Will Buckley dispossessed Brunt on the edge of the Baggies box.
Fortunately for the Northern Ireland international, the once-again impressive Scott Carson just managed to gather the ball at the second attempt after rushing off his line to challenge the Watford midfielder.
Four minutes later, Carson had to be at his best again as Adrian Mariappa found himself in acres of space inside the box from Tom Cleverley's header and saw the England shot-stopper pull off a brilliant save to deny his 15-yard volley.
Hornets manager Malky Mackay was forced into a change in the tenth minute when Lloyd Doyley limped off and was replaced by Jay DeMerit.
At the opposite end, the recalled Zuiverloon produced a superb first-time cross from the right in the 15th minute and Graham Dorrans looked certain to nod home from close range until substitute DeMerit came flying in to clear for a corner.
From the resulting flag-kick, Barnes' challenge on Scott Loach saw the Watford keeper fumble the ball goalwards but Hodson was on hand to clear from just in front of the goalline.
Back came Watford and, in the 23rd minute, Cleverley sent a 25-yard free-kick just over the bar.
Seconds later, the same man crossed from the right for Graham, whose back-post header was well blocked by Zuiverloon.
Watford had a let off in the 38th minute when Loach slipped as he attempted to deal with a long Albion ball forward.
Bednar almost got in but the Hornets keeper managed to recover and kick clear.
Four minutes before the break, the ball broke for Buckley from Eustace's challenge and he blazed high and wide from 15 yards with what was the final chance of the half.
Zuiverloon limped out of the action in the 52nd minute and was replaced by Abdoulaye Meite two minutes later.
The former Bolton defender, being watched by new Ivory Coast boss Sven Goran Eriksson in the stands at Vicarage Road, slotted in at centre-half, with Tamas shifting to right-back.
In between, Olsson's clearance fell to Mariappa and Carson did well to hold onto his fierce 20-yard drive.
Watford were forced into another change on the hour mark as Stephen McGinn came on for the injured Buckley.
Seconds later, Bednar was edged off the ball in the six-yard box as he flew in on Brunt's left-wing cross, but Albion's penalty appeals fell on deaf ears.
Bednar worked some space on the edge of the area in 62nd minute and teed up Koren, whose goalbound left-footed shot was blocked by Bennett's last-ditch slide.
Barnes then made way for Morrison as Di Matteo made a change in personnel.
The Hornets' bad luck with injuries continued in the 69th minute as Cleverley was stretchered off following lengthy treatment on the pitch after a 50/50 challenge with Olsson.
The on-loan Manchester United forward was replaced by Will Hoskins.
Cowie's long throw into the box fell nicely for John Eustace in the 72nd minute and his goalbound half-volley was blocked by Cech.
A Watford corner was headed back into the box in the 80th minute and Brunt blocked Bennett's spectacular overhead kick before Meite&nbsp;denied DeMerit's follow-up.
Albion cleared to Morrison and Harley was sent-off for a second bookable offence as he needlessly pulled back&nbsp;the Scotland international&nbsp;on the halfway line.
The game appeared to be petering out into a goalless draw - until Watford went in front with a real bolt out of the blue.
Five minutes from time, a long punt forward was nodded into the path of Graham by Cowie and he found the back of the net with a thunderous 25-yard volley, which flew just inside the left-hand post.
Albion regrouped and Morrison missed a glorious chance to level the scores two minutes from time when he fluffed wide a close-range header from Brunt's right-wing free-kick.
But there was to be one final twist - in never-say-die Albion's favour.
In a late, late bout of Baggies pressure, Brunt salvaged a point in the fifth minute of stoppage time when he got on the end of substitute Andy Slory's header across the box to nod into the far corner.
Cue delirious celebrations, both on the pitch and in the stands, as the equaliser saw Di Matteo's men inch a point closer to automatic promotion.
WATFORD (4-4-2): Loach; Hodson, Mariappa, Bennett, Doyley (DeMerit 10); Buckley (McGinn 60), Harley, Eustace, Cowie; Cleverley (Hoskins 69), Graham. Subs not used: Lee (gk), Jenkins, Henderson, Noble.
ALBION (4-5-1): Carson; Zuiverloon (Meite 54), Tamas, Olsson, Cech; Barnes (Morrison 63), Koren (Slory 80), Mulumbu, Dorrans, Brunt; Bednar. Subs not used: Kiely (gk), Cox, Miller, Mattock.
GOALS: WATFORD - Graham (85). ALBION - Brunt (90+5).
BOOKINGS: WATFORD - Harley (foul 30), Eustace (foul 35), Graham (over-celebrating 86). ALBION - Bednar (unsporting behaviour 35), Dorrans (unsporting behaviour 35), Olsson (dissent 36), Tamas (foul 90+1), Brunt (over-celebrating 90+6).
SENDING-OFF: WATFORD - Harley (second bookable offence foul 80).
REFEREE: S Tanner (Somerset).
ATTENDANCE: 14,555 (away 2,223).
ALBION STARMAN: Graham Dorrans.