Walters on Monday put pen to paper on a two-year extension, offering him the greatest security of his career with a deal through until the end of 2026.
Uncapped as an NRL player until he debut for Melbourne as a 25-year-old in 2019, Walters now has a mortgage on the Broncos No.9 jersey.
"Some players get everything at their feet but Billy has had some injuries and some disappointment," Broncos coach and Walters' father, Kevin, said.
"But he has stuck at it and worked really hard ... and now he's playing some good football for us and continuing to improve every week."
Walters' signature comes with teenage dummy-half Blake Mozer off contract at the end of next year, and Brisbane hopeful he too will hang around.
Meanwhile Gosiewski appears set to join the Broncos as soon as this week, after being granted a release from the Cowboys.
The back-rower had expressed a desire to move back to southeast Queensland for personal reasons.
He will add depth to a Brisbane pack that has lost the likes of Kurt Capewell, Tom Flegler and Keenan Paliasia since last year's grand final loss.
The Cowboys also confirmed on Monday that centre Tom Chester would miss a month of football, after suffering a hamstring injury against Penrith.
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