Paul Cooke provided the inspiration as Hull KR stormed back to register an impressive come-from-behind win at the Stoop.
Trailing 12-8 at the interval after Quins edged the opening period, the visitors ran in four second-half tries to secure a useful two points.
And it was Cooke who proved the guiding influence, scoring a try and creating three others.
With the conditions perfect for free-flowing rugby, both sides opted for the expansive approach, leading to a cut-and-thrust opening half that saw the game swing one way and then the other.
Quins took an early lead, Danny Orr's clever kick through being gathered by Matt Gardner, who powered over the line.
Moments later, though, Hull KR hit back, Cooke deceiving the defence with a long pass that allowed Kris Welham to crash over.
With both sides evenly matched, and a number of heavy hits flying in, the game continued at a breakneck pace.
The hosts were next on the scoresheet, Orr again the creator as his short pass allowed Chad Robinson to rumble over.
But back came the visitors, with a superb Makali Aizue reverse pass freeing Peter Cox to cross in the corner.
With Rob Purdham converting both tries for the Londoners, but Michael Dobson missing both kicks for Hull KR, it was Quins who had a narrow interval lead.
If the first half had been shaded by Quins, it was Hull KR who emerged the stronger after the break, producing a storming 40 minutes that secured the points.
Firstly, after Luke Gale was stripped of the ball, Cooke crashed over and, minutes later, a Cooke kick through saw Liam Colbon add another try.
With Orr failing to appear, the hosts lost all rhythm, and the visitors maintained their stranglehold on proceedings.
Ben Galea was the man to profit most, running in two late scores after good work again by Cooke.