Grenoble saw off London Welsh 20-9 at Stade Lesdiguieres to go top of Pool Five in the Amlin Challenge Cup.
Clement Darbo and Alex Davies each landed two penalties to leave the scores level at 6-6 after the first half at Stade Lesdiguieres.
Fly-half Davies edged London Welsh ahead with his third penalty but Grenoble hooker Vincent Campo responded with the opening try in the 49th minute.
London Welsh were reduced to 14 men for the final six minutes when scrum-half Nick Runciman was shown a yellow card.
And the visitors were denied a losing bonus point when Grenoble lock Andrew Farley went over in the 77th minute for the French side's second try.
The result puts Grenoble top of Pool Five on 10 points, with London Welsh in third on four points after their second defeat in three matches.
Stade Francais, with nine points from their opening two wins, have the chance to go back above Grenoble when they visit Cavalieri Prato on Saturday.
Tries: Campo, Farley
Cons: Darbo, Hart
Pens: Darbo 2
For London Welsh:
Pens: Davies 3
Yellow card: Nick Runciman (London Welsh, 74 mins)
Grenoble: 15 Joaquim Tuculet, 14 Viliame Waqaseduadua, 13 Rida Jaouher, 12 Aloisio Butonidualevu, 11 Florian Ninard, 10 James Hart, 9 Clement Darbo, 8 Flavein Nouhaillaguet, 7 Jonathan Best, 6 Fabien Alexandre, 5 Andrew Farley, 4 Thibault Rey, 3 Lotu Taukeiaho, 2 Vincent Campo, 1 Romain David.
Replacements: 16 Anthony Hegarty, 17 Gregory FabroN, 18 Karim Kouider, 19 Alexandre Pollard, 20 Valentin Courrent, 21 Henri Vanderglas, 22 Blair Stewart, 23 Fabien Gengenbacher.
London Welsh: 15 Tom Arscott, 14 Phillip Mackenzie, 13 James Lewis, 12 Seb Jewell, 11 Ashley Smith, 10 Alex Davies, 9 Nick Runciman, 8 Daniel Browne, 7 Mike Hills, 6 Lee Beach, 5 Matt Corker, 4 Adam Brown, 3 Arthur Joly, 2 Greg Bateman, 1 Tom Bristow.
Replacements: 16 Willie Hafu, 17 Billy Moss, 18 James Tideswell, 19 Mike Denbee, 20 Jon Mills, 21 Matt Keyte, 22 Simon Whatling, 23 Nick Scott.
Referee: Andrew McMenemy (Scotland)