CLAUDIO Yacob’s first-ever Albion goal looked like causing another upset and earning the Baggies a sensational Barclays Premier League double.
But Steve Clarke’s men had to settle for a draw against league leaders Arsenal – just eight days after beating champions Manchester United on their own patch.
Argentina international Yacob finally broke his Baggies duck to give the hosts the lead three minutes before half-time.
But England star Jack Wilshere’s deflected 63rd-minute strike denied the hosts all three points in a game you could argue they deserved to win.
Before that, Nicolas Anelka – back after a two-game injury absence – missed two glorious chances to punish his former club.
Wojciech Szczesny was in fine form in the Arsenal goal but Boaz Myhill was also called upon to make a couple of important saves.
In the end, the Baggies had to settle for preventing the Gunners recording a club-record ninth successive Barclays Premier League away victory.
Saido Berahino was handed his full top-flight debut as Clarke made two enforced changes to his starting XI.
The 20-year-old forward replaced the injured Scott Sinclair (hamstring) – as he did during the 2-1 victory at Manchester United.
Anelka returned from injury in place of Victor Anichebe, who failed to shake off a groin problem in time for the Hawthorns encounter.
Full of confidence from their Old Trafford victory, it was Albion who came racing out of the blocks.
But it was the Gunners who threatened first when Mikel Arteta’s fierce goalbound drive was inadvertently deflected wide by his team-mate, Olivier Giroud.
The Baggies came even closer to opening the scoring four minutes later when Anelka cleverly flicked Billy Jones’ throw-in inside to Stephane Sessegnon.
The Benin international dipped his shoulder before seeing his 20-yard strike deflect off Mathieu Flamini to force Wojciech Szczesny into a superb reaction save low to his right.
Mezut Ozil showed just why he cost £40million in the 18th minute when his pass split the Baggies defence and teed up Kieran Gibbs, who blazed well over from 12 yards.
Seven minutes later, Wilshere played a neat one-two with Giroud before firing a 20-yard shot just wide of the right-hand post.
Sessegnon looked to have broken free into the visitors’ box in the 34th minute but, although seemingly sandwiched by Gibbs and Arteta as he looked to go through, referee Lee Mason said no foul.
Five minutes before the break, Ozil’s left-wing corner found its way through to Aaron Ramsey on the edge of the box. The Wales international unleashed a powerful low drive that Boaz Myhill did well to swoop and beat out after it came through a crowd of players, and Youssouf Mulumbu was on hand to clear the rebound.
At the other end, Amalfitano delivered the ball into the box for Sessegnon on 41 and he was unfortunate to see his goalbound strike blocked by Per Mertesacker.
But a minute later, the Baggies had more joy from an Amalfitano right-wing cross as Yacob timed his leap perfectly at the near post to head into the ground and find the net despite Szczesny getting a touch on the ball.
The North Londoners were clearly rattled and seconds before half-time Wilshere was booked after going through the back of goal hero Yacob.
A blistering start to the second half saw Albion squander a fantastic chance to double their lead.
Berahino beat Jenkinson down the left before racing towards the box and firing the ball to the back post, where Anelka got the ball trapped under his feet six yards out, with the goal at his mercy.
The play immediately switched to the other end where good footwork by Giroud saw him play in Wilshere, but the England midfielder sent his left-foot strike well over from 12 yards.
A perfectly-timed run by Anelka on 52 from Liam Ridgewell’s ball down the left touchline left the French ace with a free run on goal. But the summer signing bent his finish just inches wide of the far post – much to the Gunners’ relief.
Five minutes later, Amalfitano’s free-kick finally fell to Olsson and he played it back for Berahino, whose 20-yard volley was easily gathered by Szczesny.
Just before the hour-mark, Arsene Wenger made a change as Tomas Rosicky came on for Ramsey.
The Czech Republic star made an instant impact as he turned Giroud’s pass into the path of Wilshere, whose instant 20-yard strike clipped off Olsson and past the wrong-footed Myhill to level the scores.
Clarke made a change on 69 as Anelka made way for Shane Long.
Billy Jones piled forward in the 73rd minute and let fly with a 20-yard strike that Szczesny did well to push away as it headed towards the top corner.
Moment later, Amalfitano spun in the box and was unfortunate to see his shot blocked by Gibbs for a corner.
Ozil’s pass to Giroud on 76 set the Frenchman free and Myhill did superbly to push him wide and block his shot.
A minute later, Wilshere looked set to put the hosts ahead from Ozil’s cut-back, but Mulumbu appeared from nowhere to pinch the ball off his toes with a superbly-timed sliding tackle.
The pulsating pace continued to the final whistle, with both sides endeavouring to find a winner, which never came.
However, Albion had strong penalty claims turned away in the final minute of stoppage time when Koscielny was fortunate to not be penalised for a clear shove on Long.
ALBION (4-2-3-1): Myhill; Jones, McAuley, Olsson, Ridgewell; Yacob, Mulumbu; Amalfitano (Brunt 89), Sessegnon (Morrison 78), Berahino; Anelka (Long 69). Subs not used: L Daniels (gk), Popov, Lugano, Rosenberg.
ARSENAL (4-2-3-1): Szczesny; Jenkinson, Mertesacker, Koscielny, Gibbs; Arteta, Flamini; Wilshere, Ozil, Ramsey (Rosicky 59); Giroud (Bendtner 80). Subs not used: Fabianski (gk), Vermaelen, Monreal, Miyaichi, Gnabry.
GOALS: ALBION – Yacob (42). ARSENAL – Wilshere (63).
BOOKINGS: ALBION – Olsson (foul 54). ARSENAL – Flamini (foul 22), Wilshere (foul 45+2).
REFEREE: L Mason (Lancashire).
ALBION STARMAN: Youssouf Mulumbu.