The 37-year-old played the first half of the Baggies' 5-1 win over Brighton & Hove Albion on Monday, having recovered from a thigh injury.
McAuley last played a competitive fixture in early June when lasting just 25 minutes of Northern Ireland's World Cup qualifier against Azerbaijan.
Speaking after the match with the U23s, the veteran told the Baggies' website: "It was good to get the old stripes on again after a frustrating time for me.
"Everything went well and the leg is now feeling perfectly normal again. It's been a frustrating period and obviously not ideal having my pre-season interrupted.
"It was an interesting experience. I looked around the team and felt old enough to be everyone's dad.
"But it feels good again. Now it's a question of trying to get that place back in the starting XI. The competition doesn't get any easier with the players we have been signing!"