Saracens are still in contention for a place in the Challenge Cup semi-finals despite a 26-10 away defeat against Monteferrand.
Castaignede managed a conversion and a penalty
Thomas Castaignede opened the scoring with a penalty for Saracens.
But centre Raphael Chanal responded with a try and Gerald Merceron added a conversion and a penalty to leave his side 10-3 ahead at the break.
Lock Simon Raiwalui kept Saracens in touch with a try but Pierre Mignoni responded from close-range late on.
Harlequins moved closer to a place in the last four after a 41-8 home win against Brive.
Samoan powerhouse George Harder ran in two tries while fly-half Paul Burke weighed in with 21 points.
Harder went over for his opening try in the first half to give his side a 14-3 lead at the break.
Brive's defence crumbled in the second and Harder, Tani Fuga and Simon Keogh all claimed further tries.
Brive's response was a solitary try from Jerome Naves and a Sebastien Laloo penalty, leaving coach Eric Alegret watching his side collapse to a humiliating defeat.
Zurich Premiership leaders Bath lost 24-19 away to Beziers but coach John Connolly is confident his side can overcome the defecit in the second leg.
The home side led 24-3 at half-time after tries from fullback Alain Bousquet and centre Guilluame Delmotte and a penalty try while Bath's only response was an Olly
CHALLENGE CUP QUARTER-FINALS
Saturday 24 January
Harlequins 41-8 Brive
Beziers 24-19 Bath
Narbonne 18-27 Connacht
Sunday 25 January
Montferrand 26-10 Saracens
Saturday 31 January
Connacht 16-10 Narbonne
Bath 26-7 Beziers
Sunday 1 February
Brive v Harlequins (1400)
Saracens v Montferrand (1500)
Barkley added two more goals early in the second half but it was the 75th minute before they breached the Beziers try-line through Simon Danielli while Barkley converted and added another penalty.
Connacht pulled off an excellent 27-18 away win to Narbonne after leading 24-3 at half-time despite the home side enjoying the majority of territory and possession.
Fullback Matt Mostyn, centre Darren Yapp and winger Conor McPhillips all scored tries against the run of play while veteran Eric Elwood added all three conversions.
The French club fought their way back into the match on the back of tries by backrower Gonzalo Longo-Elia and lock Olivier Olibeau as the home pack began to dominate, but Mark McHugh had the last word with a late penalty goal.