Exeter 42 Harlequins 28
Three tries in the final 20 minutes of the match sealed a famous win for Exeter Chiefs against defending champions Harlequins.
A Steenson penalty in the third minute got the ball rolling for the Chiefs and, though Nick Evans responded in kind shortly after, a converted try from Brett Sturgess, scored following a break from Luke Arscott, gave Exeter a seven-point lead.
The two teams traded further penalties in the minutes that followed before Quins put themselves back into the contest, after Evans charged down a Steenson kick to score an unconverted try.
Steenson made partial amends when he struck a penalty just before half-time, although Ugo Monye's converted try on the hooter cut the Chiefs' lead to just two points.
Many expected the tide to turn in the second period, but Exeter got off to the perfect start when Ben White burst over from close range following an eye-catching length-of-the-pitch break.
Quins hit back just before the hour when Karl Dickson crossed after Rory Clegg's interception, and the conversion from Clegg put the visitors back within two.
The match was still for the taking in the final 20 minutes and it was Exeter who were able to take proceedings by the scruff of the neck.
A quickfire Jason Shoemark brace of tries, the latter converted by Steenson, put real daylight between the sides for the first time, and there would be no Quins comeback this time.
Clegg's penalty in the closing stages pegged the Chiefs back temporarily, but Sireli Naqelevuki ensured the hosts had the final word when he bulldozed his way over the line to send the Sandy Park faithful into raptures.