The Rebels picked up their fourth win of 2016 and a first ever over the Waratahs in Sydney with a 21-17 victory on Sunday.
Building up a huge advantage by half-time thanks to tries from Jack Debreczeni and Toby Smith, the Rebels failed to score any points in the second half as the Waratahs hit back through scores from Jack Dempsey and Matt Carraro, but the hosts fell short of changing the outcome.
Composed in attack and solid in defence, this was another example of how much progress the Rebels have made over the last two years as they picked up their third away win of 2016 with a workmanlike performance.
Head coach Tony McGahan though will have to be concerned at how his side went into the shell trying to protect the lead with a whole quarter left to play.
Atrocious discipline and basic handling errors left the Waratahs chasing the game, just as they did against the Highlanders, as once again their late surge proved not to be enough.
Israel Folau's 50th Waratahs appearance, on his 27th birthday, turned out to be one to forget. The Wallabies full-back was sin-binned ten minutes before half-time for cynical play.
The Rebels wholly deserved to be up 21-3 at the break after the "rubbish" served up by the Waratahs - the words of their head coach Daryl Gibson - following a lacklustre opening 40 minutes.
Debreczeni struck with an early penalty after his opposite man Bernard Foley strayed offside, but the Waratahs fly-half responded eight minutes later off the tee to tie the scores.
Continued infringements however put the home side under immense pressure, with the Rebels consequently producing the game's first try through their number ten.
Debreczeni used his sizeable frame to power over from close range after the Rebels accumulated the phases inside Waratahs territory, with Debreczeni busting through a tackle to make it 8-3.
Playing full of confidence, as they often have away from home this season, the Rebels continued to threaten with a second try coming soon after.
Lopeti Timani showed off his power and skill by fending off the tackle of Angus Ta'avao before timing his pass well to the supporting Smith, who cantered over under the posts. Debreczeni's conversion opened up a 12-point lead.
Matters were made worse for the Waratahs by a yellow card for a professional foul by Folau, scrambling back in defence, as Debreczeni's boot knocked over two quick penalties before the break to give the Rebels that commanding 21-3 advantage heading down the tunnel.
The Waratahs urgently needed a response to set the tone for the second half and it came 12 minutes in, blindside flanker Jack Dempsey crashing over after a rare error at the set-piece from the Rebels set the Waratahs up to attack. Foley converted to make it 21-10.
Too often the Waratahs paid the price for a poor final pass after good work in the build-up, with attacks routinely ending with knock-ons or by the Rebels pouncing at the breakdown.
Calling on the power of Will Skelton, Sam Lousi and Wycliff Palu off the bench the Waratahs began to make in-roads in attack, only to again be turned over, as the home crowd at Allianz Stadium grew frustrated.
Matt Carraro's try not long after however brought the contest back to life. After a half-break up the middle from replacement scrum-half Matt Lucas, the Waratahs went to the wing through a chip kick by Foley, finding Reece Robinson whose pass infield set Carraro on a run to the line.
Now the Waratahs were enjoying all the possession and territory, as the Rebels began to fade in their bid to protect a shrinking lead.
Good defence and a late scrum penalty inside the Waratahs half though clinched the win though for the visitors, Debreczeni missing a late kick but winding the clock down as the Waratahs failed to come up with a winning try.