With several first-team players away on international duty or being kept in bubble wrap amid the Gunners' Premier League and Champions League title fight, a squad largely comprising academy prospects took to the field at QPR's TSG Elite Training & Performance Centre.
However, the injury-plagued duo of Partey and Tomiyasu added some experience to the ranks, although their presence was for nought as the North London giants shipped four without reply to their Championship counterparts.
Michael Frey gave the hosts the lead heading into the break, and the 29-year-old notched his second of the match in the second half before Elijah Dixon-Bonner and Ziyad Larkeche completed the R's rout.
Partey saw the field for 64 minutes on Thursday, as the Ghana international continues to work his way back to full fitness following the thigh injury which had sidelined him for nearly five months from October to March.
The former Atletico Madrid man missed the Africa Cup of Nations as a result of his surgery, and he asked to be left out of Ghana's squad for their March fixtures in order to continue his rehabilitation with the Gunners.
Partey has only made seven competitive appearances for Mikel Arteta's side in the current campaign, and the Gunners are expected to entertain bids this summer before his contract expires in the summer of 2025.
Meanwhile, Tomiyasu - whose time in North London has also been blighted by injuries - completed the first half of the four-goal thumping the day after his new long-term contract at the Emirates was announced.
The former Bologna man is a trusted performer by Arteta when fully fit and quickly won over his fans and teammates, but he has not played for the club since New Year's Eve owing to two injuries either side of the Asian Cup.
After recovering from a calf concern, Tomiyasu sustained a knock while representing Japan at the continental tournament, although he was back on the bench against Porto at the Emirates.
As well as Partey and Tomiyasu, highly-rated academy duo Amario Cozier-Duberry and Myles Lewis-Skelly also started the loss to QPR, while Salah-Eddine Oulad M'Hand came on as a second-half substitute.
Arsenal are leading Liverpool on goal difference at the top of the Premier League table and return to action after the international break with a mouthwatering clash away to Manchester City on March 31.
However, the Gunners have been handed a significant injury concern with Bukayo Saka ahead of the trip to face the champions, who are just one point behind Arteta's men in third place.