Derby County struck twice in the final few minutes to deny Albion's youngsters their first PL2 victory of the season on Bank Holiday Monday afternoon.
Jack Bray's brace and Ollie Bostock's strike put the visitors 3-0 up before the hour in the East Midlands, but Jayden Davidson's quickfire double inside the final 15 made things uncomfortable for Leigh Downing's outfit.
Bostock then got his second, but efforts from Charles Agbawodikeizu and Sean Corry in the 88th and 90th minute respectively left the Baggies incredibly frustrated on a day where first-team midfielder Tammer Bany completed the opening half.
The first period was one of few opportunities. Striker Bray and left-back Adam Letlat had early openings, but their shots were deflected out for corners.
At the other end, centre-back Noah DuPont dived in to make a tremendous tackle, knocking the ball away from County's number four and captain Adisa Osayande, who looked destined to score.
The half was heading for a close without any goals, but Bray and the Baggies had other ideas. The forward bagged himself two in two minutes right before the interval.
He weaved his way in and out of challenges from Rams players and found the bottom corner to make it 1-0, before pouncing from close range following a DuPont nod down to double the lead moments later.
Bostock added a third goal eight minutes into the second half. Albion broke at speed and worked the ball out wide to the winger, with Ollie cutting in and finding the bottom corner with a precise finish.
Derby dug deep though and put up a fight despite being 3-0 down. Substitute Davidson grabbed one back with 15 minutes left on the clock when the ball fell kindly to him inside the area, and he rifled home.
The same man was on the scoresheet less than 90 seconds after that, notching his second with a terrific curling effort from the best part of 30 yards out.
The Baggies thought they had the points wrapped up when Bostock registered his second and his side's fourth seven minutes from the end. The 19-year-old spun in the penalty area and saw his volley hit the post and fly in to make it 4-2.
However, once again, the Rams rallied and scored twice to steal a point courtesy of two second-half substitutes. Agbawodikeizu rolled the ball into an empty net after a disappointing error from the away team at the back, and Corry blasted beyond Brian Okonkwo in the Albion net deep into stoppage time to prevent Downing's group from securing their maiden triumph of the new league term.
Albion: Okonkwo, Iddrisa, DuPont (Mohammed 73), Pinnington, Letlat, Bany (McNeil HT), Deeming (Blackshields 61), Crowther, Bostock, Parmar (Colesby 69), Bray (French 69).
Substitutes: Rutter (GK), Maughan.
