A 40-metre try to Corey Oates in the 61st, a Kahu penalty goal in the 66th, and an Anthony Milford field goal in the 77th, sealed Brisbane's eighth win of the season and restored their position to a share of the competition lead.
For the Knights, the loss was their sixth defeat in their past seven games.
Broncos five-eighth Anthony Milford opened proceedings on a Reed offload in just the 4th minute, only for Newcastle's Kade Snowden to execute a similar play for Chad Randell seven minutes later.
Dominant in possession and field position, Knights forward Korbin Sims seized the initiative by carrying four defenders over the line in the 18th before Joseph Leilua also made short work of a lazy defence by barging over one off the ruck.
But the visitors set up the comeback on the stroke of halftime when a Ben Hunt grubber popped up perfectly for Reed to keep them within striking distance at the main break.
After receiving texts of praise from the club's Origin representatives post-game, Broncos coach Wayne Bennett described the win as a "club" victory.
"We had nine players missing there tonight," Bennett said.
"But I've been in that situation a lot of times at the Broncos and learnt a lot of things on the journey.
"We've got a club, we just haven't got the team, and that's what was proven here tonight.
"We'll need those boys at other stages this year so it just gives everybody confidence about what we're doing and how the system is working for us."
The Broncos had six players away on Origin duty, and at least another three on the injured list.
Making matters worse, the team could be without young gun Kodi Nikorima after he sustained a knee injury in the second half that is likely to rule him out for up to a month.
But Bennett's baby Broncos stood up to the challenge and closed out a win with maturity beyond their years.
"They don't expect to lose. That's not in their DNA, these fellas," Bennett said.
"My previous experience with all this is from the time you get four players-plus missing, you become vulnerable.
"And the more players you got missing, the more vulnerable you become.
"In my mind it made the victory even better than the fact that we had so many players out."
Knights coach Rick Stone bemoaned the early onslaught in the second half that cruelled their chances of winning.
"It really put a dent in us and took a wind out of our sails," Stone said.
"They controlled the game really well in the second half.
"We just gifted the start to them with the momentum and they took advantage of it and pretty much kept the foot on the throat the rest of the half."
- AAP
