The 15-point winning margin on Sunday ensured that Martin Johnson's men advance on the back of a 12-point aggregate win, after Quins narrowly defeated double Heineken Cup winners Leicester by just three points (26-23) at The Stoop on Wednesday night.
The winners of the Wildcard Final on May 31 will ultimately qualify for next season's Heineken Cup.
It was Quins who opened the scoring in the fifth minute, with fly-half Paul Burke slotting and early penalty.
Sarries managed to keep Leicester Tigers at bay for almost 15 minutes, before fullback Tim Stimpson slotted a penalty to level the scores.
When winger Ugo Monye went over for the first try of the match in the 25th minute, and Burke added the conversion, it seemed as if Quins were beginning to take control – in the match and on the aggregate scoreboard.
But 10 minutes later Leicester stormed back into the game with a Glen Gelderblom try, while Stimpson added the conversion to make it 10-all on the day and Quins just three points clear on aggregate.
A 38th minute Stimpson penalty put the Tigers ahead on the day and level on aggregate – which is where the match stood at the break.
It was again Stimpson who scored next, a 45th minute penalty. But Leicester opened a slight gap – on aggregate by eight points and on the day 21-10 – when Neil Back scored a try in the 57th minute.
But Quins had enough fight left in them and in the 63rd minute Burke pulled it back to 21-13 on the day and just five points on aggregate.
But it was Leicester who scored next, with outside back Will Skinner scoring what turned out to be the final nail in the Quins coffin in the 77th minute. Stimpson added the conversion for a 28-13 lead (12 points ahead on aggregate).
For Leicester:Tries: Gelderblom, Back, SkinnerCons: Stimpson 2Pens: Stimpson 3
For Harlequins: Try: MonyeCon: Burke Pens: Burke 2