He was crucial in setting up their first points of the season to Clinton Gutherson.
But without their first-choice pair, the Eels were rudderless with the ball in the second half, back-up Luke Kelly and fill-in Kenny Edwards struggling to find any gaps in an organised Broncos defence.
Still, Parramatta kept turning up with impressive defence to restrict the Broncos to just a penalty goal and a field goal in the second half.
At one stage, Michael Jennings almost came up with a try in his club debut but the referees' bunker - also on debut - correctly and swiftly ruled double movement.
But the visitors showed why they're the competition favourites, seeing off a number of raids on their tryline to secure the victory.
Earlier, Brisbane five-eighth Anthony Milford finished off an early entry for highlight of the season, completing a 60-metre try that began with a Corey Parker offload and included a chip ahead from Oates.
Jordan Kahu nabbed the opening try of the season before succumbing to a quad injury in the first half.
Broncos coach Wayne Bennett said that while his team was rusty in attack, they controlled the game with their defence.
"It was a bit shaky there a couple of times but we can fix those things pretty easy. Overall I was pretty pleased with (the defence)," Bennett said.
"At the end of the night, it's what won it for us and kept us in the game. We didn't have a great number of points in us tonight but it's about defence, it had to be good."
Eels coach Brad Arthur didn't want to dismiss the performance just because his team was minus their starting halves for half the match.
"Regardless of losing a couple of halves, we only completed at 50 per cent in the second half. We just needed to be a bit more patient," he said.
"But if we want to take a positive out of it, even though we were a bit loose at times through the middle with our defence, we scrambled okay and kept them out in the second half."
- AAP
