The midfielder st ruck an 89th-minute equaliser to clinch a 1-1 draw after Nacer Chadli looked to have condemned his former club to defeat
Chadli, the Baggies' £13million record buy from Spurs in the summer, rammed in with eight minutes left to put the hosts on the verge of a smash and grab
But Alli turned in a scrappy leveller and Albion were also indebted to goalkeeper Ben Foster after he stopped Spurs from running riot in the first half
The England international twice saved from Alli and also denied Erik Lamela, Ben Davies and Christen Eriksen
Foster needed to be at his acrobatic best with Spurs in complete command from the start as Lamela and Vincent Janssen combined for the former to drag his shot across goal
Eriksen then fired straight at Foster in the opening 15 minutes as Tottenham probed without exploiting Albion, the hosts planting 10 men behind the ball at all times
It worked with the visitors restricted to efforts from distance as Davies' drive deflected wide and Eriksen fired off target before they were left frustrated by Foster three times in eight minutes.
The keeper raced out to save at Alli's feet after half an hour and then turned Davies' effort wide as Spurs began to turn the screw
Alli then acrobatically sliced off target and blew an even better chance after 38 minutes when Foster again came to the Baggies' aid
Janssen showed good strength to shield the ball and sent Alli racing clear but with just Foster to beat the midfielder's tame effort was beaten away
And the England international kept the Baggies level again three minutes before half time, turning Eriksen's rasping low strike behind after Albion had been opened up by neat interplay
Yet, after Foster's heroics the hosts could have gone into the break ahead
They had been anonymous as an attacking force with Salomon Rondon a lonely sole striker but the Venezuela international almost cashed in when Hugo Lloris spilled James McClean's low shot
Albion almost made a mockery of Spurs' dominance again two minutes after the re-start but Gareth McAuley failed to get a telling touch on Chadli's corner
Slowly, the Baggies began to offer more than just their steely first-half resistance and Tottenham's plans were further skewed when Toby Alderweireld was stretchered off following a collision with Rondon and replaced by Eric Dier
Spurs had failed to find their first-half rhythm and, although Moussa Sissoko's deflected effort dropped just wide after 62 minutes, their level had dropped significantly since half time
Emboldened, Albion grew into the game and began to unsettle the visitors who had failed to adjust to losing Alderweireld a nd with eight minutes left they shocked Spurs
Jan Vertonghen cleared underneath his own bar and from the resulting corner Lloris turned McClean's shot onto the post and Chadli slammed his fourth goal of the season into the roof of the net
But Alli finally beat Foster with a minute left when Eriksen's shot deflected into his path and he stabbed in from 10 yards
Eriksen also almost won it in stoppage time when Foster turned his deep free-kick over
Source : PA
Source: PA