Edinburgh snuck past Harlequins 36-35 in a thrilling encounter at Murrayfield.
The Scottish side ran in five first-half tries to take a 31-14 lead at the break. A Harlequins fight back saw them go ahead before a Tom Brown effort in the 73rd minute clinched the win for Edinburgh.
Jonny May was among the try scorers for Gloucester as they ran out 30-8 winners over Benetton Treviso at Kingsholm. The winger made his first appearance since December after a long injury layoff.
Lewis Ludlow, Matt Scott and Callum Braley also crossed for the home side as they join La Rochelle at the top of pool 1.
Brive edged Worcester Warriors 25-24 at Sixways. Tries from Takudzwa Ngwenya, Said Hireche and Thomas Acquier clinched the win for the home side, while Ben Te'o and Andy Short crossed for Worcester.
Russian side Enisei-STM claimed a second British scalp in eight days, with a bonus-point 38-18 home win over Newport Gwent Dragons in the European Rugby Challenge Cup.
Enisei-STM last Saturday defeated Worcester Warriors 19-12, but this win takes them top of Pool Three at least until the next round in December.
Hooker Stanislav Selskii scored a brace of tries and there were also touchdowns for Iuri Kushnarev, Dmitrii Gerasimov and substitute Valery Mrozov at the Trud Stadium in Tomsk - more than 4,200 miles from Newport.
Newport, who trailed 17-12 at the break, scored two tries through backs Pat Howard and Sam Beard.
In the evening kick-off, teenage Ospreys winger Keelan Giles enjoyed another European night to remember as he scored a hat-trick of tries in a 31-13 win in Lyon.
The 18-year-old notched twice as Ospreys thrashed Newcastle 45-0 in their competition debut last time out and he was back among the tries again on Saturday, going over for converted scores in the 14th, 29th and 45th minutes.
Replacement Sam Parry added a fourth try late on -- fly-half Sam Davies again slotting over the extras for a personal haul of 11 points with the boot -- as Ospreys made it back-to-back wins in Pool Two.
The Welsh side now boast a five-point lead over Lyon at the top of the group after inflicting a first defeat on the French outfit, who scored second-half tries through Curtis Browning and Franck Romanet.