Albion took their points tally to seven from a possible nine at the start of the season as they followed up their opening-day win over Liverpool with another emphatic victory.
Long made it three goals in four days - after his brace at Yeovil in the Capital One Cup - as he converted a low cross from substitute Peter Odemwingie before McAuley headed home from a set-piece to condemn Everton to a first league defeat since March 24 against Swansea.
Albion were good value for their win with James Morrison and Youssouf Mulumbu controlling the midfield and McAuley a rock-solid performer in the heart of the defence.
Everton were left to regret two missed opportunities by Marouane Fellaini at the start of the second period, but they could have no complaints with the result after lacking a cutting edge over 90 minutes.
Everton controlled the early stages and McAuley blocked a shot from Steven Pienaar.
Nikica Jelavic got on the end of a corner from Leighton Baines and was disappointed to send his near-post header well wide.
The Toffees suffered a setback when midfielder Darron Gibson pulled up suddenly and had to be replaced by right-back Tony Hibbert with skipper Phil Neville switching to the centre of the park.
Everton goalkeeper Tim Howard dealt comfortably enough with a dipping attempt from Steven Reid but Albion came close to taking the lead after 29 minutes.
Left-back Liam Ridgewell supplied a teasing cross which was met by Baggies striker Shane Long and his header thumped against the crossbar.
Hibbert became the first player to be booked after 36 minutes for a late challenge on Marc-Antoine Fortune.
Everton continued to look the more composed on the ball and Fellaini peeled away from his marker at the far post only to send his header over the bar from a Hibbert cross.
But Albion again went close a minute before half-time. Morrison made a probing run and, after cutting inside, found himself with only Howard to beat. But the American stood up and beat away a fiercely struck shot from the midfielder who had recovered from an ankle injury to play.
Reid was booked two minutes into the second half for a mis-timed challenge on Pienaar before he limped out of the action to be replaced by Billy Jones.
Fellaini had Everton's best chance to that point after 55 minutes after Neville had headed a clearance from Ridgewell back into the box. He turned sharply enough to create the opening but dragged his shot across the face of goal.
The Belgium international spurned an even better opportunity five minutes later when he side-footed over from 10 yards after racing onto a low cross from substitute Kevin Mirallas.
It proved a costly miss as Long broke the deadlock after 65 minutes. Ridgewell found Odemwingie in space on the left flank and his low cross picked out Long who got in front of Sylvain Distin to steer the ball past Howard.
Distin, Neville and Fellaini were all booked in quick succession for fouls as Albion looked to turn the screw.
Argentinian midfielder Claudio Yacob was only inches wide with a fierce long range drive and Howard tipped over a powerful shot from Mulumbu.
But with seven minutes left McAuley sealed the win with his glancing header from a Chris Brunt corner.