Leaders Clermont notch 70th straight home victory
Clermont's French flanker Julien Pierre (up) grabs the ball in a line out during the French Top 14 rugby union match ASM Clermont Auvergne vs Oyonnax on December 29, 2013 at the Marcel Michelin stadium in Clermont-Ferrand
Fijian born wing Noa Nakaitaci was the architect in the first half, scoring a brilliant 60-yard individual try before making a second break and teeing up Samoan No.8 Fritz Lee to go over.
Nakataici's score was pure genius as he took the ball from the back of a breakdown, looped around the forwards and burst through a gap in Oyonnax's defensive line before chipping ahead and winning the foot-race to touch down.
However, Clermont were denied a bonus point by a spirited second-half display from the second division champions.
Centre Pierre Aguillon and South African hooker Jody Jenneker both went over either side of France hooker Benjamin Kayser's try for the hosts to at least demonstrate third-from-bottom Oyonnax's ability to cause problems at this level, although the lack of a bonus point keeps them hovering perilously just three points above the relegation places.
Clermont moved provisionally six points clear at the top.
Stade Francais recorded their third successive home success with a 19-12 win over Perpignan in a scrappy and hot-tempered encounter.
Victory saw Stade move into second, although they could yet drop to fourth before the weekend is up.
"That is what we wanted, three straight wins at home," said Stade captain Sergio Parisse.
"It was tough going out there against a solid and resilient Perpignan side but we just about deserved to keep our heads in front.
"Now we have Biarritz away and we want to confirm our form there, though it won't be easy."
Stade and Perpignan exchanged penalties early on but it was the Parisians who gained the advantage that they never let go when, against a Catalan side reduced to 14 men and their scrum taking a pounding, the hosts were awarded a penalty try.
Perpignan's Welsh star James Hook -- given a rare start at fly-half as he has this season usually started at fullback -- scored four penalties but was matched by his opposite number Jerome Fillol, who also added a conversion for a 14-point personal haul.
Grenoble maintained their own fine home form and ended Castres's three-match winning run with a 20-16 success that could see the champions drop as low as fifth by the end of the weekend.
Tries from South African prop Albertus Buckle and Fijian wing Alipate Ratini gave Grenoble victory despite Fiji centre Seremaia Bai's score for Castres, who had to content themselves with a losing bonus point.
Montpellier bounced back from three straight defeats to get their top six bid back on track with a crushing 48-22 destruction of rock-bottom Biarritz, who are becoming increasingly isolated.
Tries from Fiji wing Timoci Nagusa, hooker Mickael Ivaldi and braces from New Zealander No.8 Alex Tulou and Georgian flanker Mamuka Gorgodze ensured an attacking bonus point.
That was despite spirited resistence from Biarritz midway through the second period as Norway lock Erik Lund, American wing Takudzwa Ngwenya and South African fullback Johan Pietersen all crossed the whitewash.
Bordeaux-Begles earned a crucial victory to ease nine points away from danger with a 27-23 win over fellow strugglers Brive, who are five points above the drop zone.
South African lock Jandre Marais scored twice while Fijian fullback Metuisela Talebula added a brilliant breakaway score, while Brive replied with tries from Australian wing Alfie Mafi and fullback Gaetan Germain.