Jonny Wilkinson added 13 points for Toulon with a near faultless kicking display before being replaced with six minutes remaining, with opposite number Stephen Jones slotting four penalties in reply for the Scarlets.
A brace of scores from Clement Marienval gave Philippe Saint Andre's men a 23-6 lead just after half-time before three further tries in the final seven minutes gave the scoreline a comfortable feel.
Jeremy Sinzelle joined his wing partner on the scoresheet with 73 minutes gone and New Zealand Rugby League convert Sonny Bill Williams added a fourth with five minutes left.
Man-of-the-match Olivier Missoup made it five on the final whistle as Toulon breezed into their first European semi.
Earlier on at the Sportsground in Ireland, Miah Nikora drop kicked Connacht into the final four a 78th minute strike that secured a famous win over last season's beaten finalists.
The Irish province took full advantage of Benjamin Boyet's sin binning to reverse a 20-14 deficit with 15 minutes to play.
NIkora did what Brock James failed to do yesterday, as he slotted the late winner for his team.
It means a seventh straight win in this competition for Micheal Bradley's side, who now are just 80 minutes away form their first Amlin Challenge Cup final, after twice falling at the semi-final stage in the past.
Conditions in Galway were perfect and the players delivered another nail-biting European occasion - hot on the heels of the thriller in Dublin. Again, it was the Magners League side who came away with the victory, but it could have been a very different story as the French side threatened to spoil the party.
They had fought their way back from a half time deficit of 14-10 to lead by 20 points to 14 before Boyet was sent to the sin binning for killing the ball.
It meant the Irish side were able to halve the difference and then hammer home their numerical superiority with a second penalty.
Spurred on by vociferous home support, they pressed ahead. But Nikora needed two bites at the cheery to clinch victory. His effort of the 77th minute was struck sweetly enough but it did not have the accuracy to affect the score.
The same can't be said for his final effort and his side will now look to the semi-final in the first week of May.