Two tries by fullback Mike Brown secured a stunning win for the Harlequins rugby club at Toulouse blowing Pool Six wide open ahead of the final two Heineken Cup group matches next month.
The 31-24 victory lifted the English Premiership leaders to second place in Pool Six, one point behind four-times European champions Toulouse who top the standings with 13.
Earlier two penalties from Ireland first five Ronan O'Gara helped Munster edge Scarlets 19-13 and move five points clear at the top of Pool One.
Northampton's emphatic 45-0 win over Castres increased the possibility of the last year's Heineken Cup runners-up qualifying for the Challenge Cup by finishing third in Pool One.
Defending champions Leinster continued their unbeaten run with a classy 52-27 win over Bath, going six points clear at the top of Pool Three.
Pool Four is very tight with Ulster, Leicester and Clermont Auvergne separated by just three points after four matches.
Ulster defeated Aironi 46-20 to go top with 14 points and Leicester overcame a nine-point deficit against Clermont to win 23-19 in a pulsating game that lifted the English side to second place, two points behind the leaders.
The fifth round begins on January the 13th.