Dave Rennie has made nine personnel changes to the starting XV for the visit of the defending champions, with new signing Aki Seiuli in line for a potential debut from the replacements bench.
Gray is partnered by fellow Scotland international Tim Swinson in the second-row, with the latter also returning to the starting lineup.
Robert Harley shifts from the second-row to the flank, lining up alongside Chris Fusaro and Ryan Wilson.
Ali Price makes his first start of the season at scrum-half, with Peter Horne starting outside him at fly-half.
Former Highlanders prop Seiuli is included in a matchday 23 for the first time since arriving at Scotstoun, with the man from Christchurch joined by Grant Stewart and Adam Nicol as the front-row replacements.
Speaking following the announcement, Rennie said: "It's good to have Ali back starting this weekend - he obviously had an extremely disappointing injury at the World Cup, and he's worked hard to get back to full fitness. He's had a couple of cameos off the bench, and he's ready to go.
"Leinster have great depth and have been the form team in the competition. They are very well coached, are playing with great confidence and have threats across the park. We'll need to be at our best to get a result.
"A packed Scotstoun is a special place to play at. The crowd are vocal and engaged and remind us that we're playing for something bigger than ourselves."
Not available due to injury: Siua Halanukonuka (calf), Scott Cummings (knee), Bruce Flockhart (knee), Jale Vakaloloma (shoulder), Callum Gibbins (shoulder), Sean Kennedy (foot), Lee Jones (calf), Ratu Tagive (hamstring) and DTH van der Merwe (knee)