Tries either side of the break from Vasily Artemyev and Scott Armstrong twice put the Wanderers ahead, but they were left to count the cost of a first half interception that kept Quins level after a home dominated 40.
The hosts were quickly in front, as a couple of grinding mauls were followed by Alex Waller swatting away Rory Clegg and moments later Artemyev cut through from 25 metres out to slide under the sticks.
Quins replied quickly through a Rory Clegg penalty though and the fly half would be back at the tee for the simplest of conversions just moments later, Charlie Walker picking off a floated Wanderers pass and coasting home unopposed.
Tonks would slot one of his next two shots at goal to bring the hosts level, thumping an upright with the other and almost setting up an overlap with a swift break. Artemyev also went close to his second in the corner but Tonks' three points would prove to be the last of the opening 40.
The Wanderers skipper was at the forefront again as the second half started, inexplicably denied a certain try by referee Martin Fox and cracking another post with the penalty play was pulled back for. The frustration only lasted a matter of minutes, however, Tonks again providing the break that allowed Jon Clarke to release Armstrong.
It was no more than the Wanderers deserved and with the extras added, the lead was theirs for the first time since the seventh minute. Clegg closed the gap with his second penalty of the night but missed with his next, an ugly hook from 35 metres that glanced the post.
His next chance was unmissable though, the Quins pack doing a number on the Wanderers to earn a penalty try - the visitors coming more and more into the contest. A marginal offside call was almost punighed by Clegg, his attempt falling narrowly short and another went left of the target shortly after.
Unfortunately for the Wanderers, the Quins fly half wouldn't be made to pay for his misses, the by now vastly more experienced visitors winding down time in opposition territory and Karl Dickson ending a good Wanderers season at the semi-final stage.
3mins WAND Try Artemyev Con Tonks 7-0
7mins QUINS Pen Clegg 7-3
9mins QUINS Walker Con Clegg 7-10
14mins WAND Pen Tonks 10-10
30mins WAND Miss pen Tonks
HALF-TIME WAND 10 QUINS 10
48mins WAND Miss pen Tonks
50mins WAND Try Armstrong Con Tonks 17-10
56mins QUINS Pen Clegg 17-13
60mins QUINS Miss pen Clegg
64mins QUINS Try Penalty Con Clegg 17-20
70mins QUINS Miss pen Clegg
72mins QUINS Miss pen Clegg
FULL-TIME WAND 17 QUINS 20