Arthars trained at left wing for the full Broncos training session on Sunday while Oates trained with the club's secondary group.
The 25-year-old Arthars did not play in the round 26 win over Canberra, when he was 18th man as Oates played his 200th NRL match.
Arthars then played centre, with Oates on the wing, in the 32-22 loss to the Storm on Thursday night.
Oates has had an injury-interrupted season, playing just nine games.
Arthars has been outstanding through 17 matches, making 14 line breaks and scoring eight tries.
Brisbane captain Adam Reynolds (calf) and prop Pat Carrigan (foot) trained well on Sunday as they seek to return from injury.
The pair worked on their own away from the main group before joining team drills and moving freely.
Second-rower Jordan Riki trained in a red no-contact bib but was with the starting 13 when the session ramped up.
Coach Kevin Walters has a crucial decision to make about his four-man bench but from the session on Sunday the front runners appear to be hooker Tyson Smoothy, second-rower Brendan Piakura, prop Corey Jensen and versatile forward Kobe Hetherington.
Club legend Oates is off-contract and has a one-year extension on the table from the Broncos for 2024.
The 28-year-old said it had been "a s*** year" in many respects, but that had not diminished his love for the club where he has wanted to stay since he was a teenager.
"I have made it pretty obvious in my career that the Broncos is always my place," Oates said.
"But the way it works these days, if you have to move on, you have to move on.
"I will wait and see what happens the next few weeks, but I'm just enjoying playing footy.
"I have been injured a lot this year and I want to go out and prove that I'm still worth it and I can still put the performances in and do my job.
"It's not hard being off-contract. I've done it five times, so it's alright."
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