Leon Barnett repaid a slice of his £3million transfer fee for the Baggies as he rescued a point for them at the Hawthorns.
Central defender Barnett, snapped up from Luton Town during the summer, capped a stirring fightback with a 73rd minute strike.
Albion had been trailing from the 27th minute after Ryan Shawcross's third goal of the season had given a rugged Stoke side, who are unbeaten in five games, the lead.
Colchester bounced back from their 1-0 loss to Scunthorpe at the weekend as they recorded a fine 4-2 home victory over managerless QPR - the Rs, who sacked John Gregory during the week - remain rooted to the foot of the table with just three points from their opening nine games of the season.