Aviva Premiership Venue: Twickenham Date: Saturday 2 September Kick-off: 16:45 BSTCoverage: Full match commentary on BBC Radio 5 live and BBC Radio Berkshire and live text commentary and score updates on the BBC Sport website
Second-row Franco van der Merwe will make his Irish debut in the London Double Header fixture after finalising his move to the club on Thursday.
Petrus du Plessis will also start his first game for the club after signing from Saracens in June.
Harlequins’ teenage fly-half makes his Premiership debut, while full-back Mike Brown will match Nick Easter’s record of 281 club games.
Former Bristol forward Ben Glynn makes his Harlequins debut at lock.
London Irish return to the Premiership after a year in the second tier, while Harlequins finished sixth last year.
London Irish director of rugby Nick Kennedy told BBC Radio Berkshire: “We’re really excited to be back in the Premiership and as always, after a long pre-season, you just want to get out there and play.
“As a squad, we’re really looking forward to it. There’s a lot of excitement around the guys who get that first chance this season to take the club forward.
“Harlequins have threats all over the park with livewires everywhere and we’ve got to be on our mettle all the time.”
London Irish: Bell; Lewington, Hearn, Mulchrone, Ojo; Marshall, Steele; Hobbs-Awoyemi, Paice (capt), Du Plessis, van der Merwe, De Chaves, Coman, Cowan, Treviranus
Replacements: Porecki, Reid, Franks, McNally, Gilsenan, McKibbin, Tonks, Tikoirotuma.
Harlequins: Brown; Yarde, Marchant, Roberts, Walker; Smith, Care; Marler, Buchanan, Collier, Glynn, Horwill (capt), Robshaw, Ward, Clifford.
Replacements: Gray, Lambert, Sinckler, Merrick, Luamanu, Mulchrone, Catrakilis, Stanley.