Roy Hodgson's men picked up a valuable win thanks to an excellent performance, with their former Ipswich defender popping up with only a few minutes to go.
West Brom had the better of the first half as it continuously pressed high up the pitch, affording Chelsea next to no time on the ball, but the visitors were holding firm and Petr Cech was on form.
The second half followed a similar pattern as West Brom dominated long periods and its i goal finally came as McAuley poked home following a free kick.
Both sides named unchanged teams from their respective wins last weekend and Fernando Torres missed out once again for Chelsea, while Daniel Sturridge also started despite being a doubt with a toe injury.
After five goals in his last two matches, Peter Odemwingie started up front alongside Marc-Antoine Fortune. Jerome Thomas started even though he was doubtful and Chris Brunt returned to the squad, taking a place on the bench.
The match started brightly for both sides as first Keith Andrews’ header almost tested Cech, and then moments later at the other end Gary Cahill tried to bundle the ball home after Juan Mata’s corner, but the home defense stood strong.
The hosts weren’t allowing Chelsea any time in possession as they pressed the club with intent, and after robbing Ramires of the ball in the center circle, they carved open another chance as James Morrison’s long-range effort was tipped over the bar by Cech.
Chelsea had been second best for the first 15 minutes, but it soon got itself a real chance. Michael Essien played a forward ball to Didier Drogba, who in turn flicked the ball cleverly into the penalty area, but Mata’s right-footed attempt was put behind by Ben Foster.
Next to try his luck was Marc-Antoine Fortune as his effort squirmed wide of Cech’s right-hand post, followed soon by a long-range strike from Odemwingie, which also went wide.
With Chelsea offering more in attack, West Brom continued to give as good as it got. Thomas looked particularly lively down the left wing, beating Ramires easily time and time again, while Andrews again went fairly close with a header, but still there was no breakthrough.
The back-and-forth nature of the match continued as Chelsea was twice unlucky not to take the lead. First, Essien’s driven strike was clawed away from the top corner by Foster, and then Sturridge, with the defense and goal at his mercy, beats the goalkeeper, but puts his strike wide of the post. And despite a late effort from Youssouf Mulumbu, the first half ended goalless.
The second half started in a similar to vein to the first, as both sides traded blows, with neither team managing a goal.
Referee Mark Halsey received a massive cheer as he overturned his linesman’s decision to give Chelsea a free kick, subsequently giving West Brom the set piece from which it almost scored as Odemwingie was crowded out.
However, Chelsea went straight down the other end and almost took the lead. Steven Reid gave possession away before going down injured, but the visitors weren’t interested as Drogba played Sturridge though the middle, only for Foster to rush miles out of his goal, beating the striker and clearing.
Fortune soon got himself another opportunity as a ball from the left evaded Luiz, bouncing over the Brazilian, but the Baggies striker’s shot was palmed over by Cech. By now the match was fast and furious, but neither goalkeeper was giving in.
West Brom really began to boss the match with around 30 minutes to go, but Cech continued to keep out the hosts. Fortune was at the fore once again as he tested the keeper from the edge of the box, then moments later Ashley Cole cleared his lines just before Morrison could head home for the Baggies.
As the hosts continued press, a goal always looked likely and they finally took the lead through McAuley. Chelsea once again failed to clear its lines from a West Brom free kick and after the ball bobbled about in the penalty area, the former Ipswich defender was on hand to poke the ball past Cech.
Frank Lampard came inches from equalizing as he flicked Mata's pass goalwards, but West Brom held on for the three points after a fantastic performance.