From Muppet Wiki

The names and voices of Oscar the Grouch around the world. Like Big Bird, Oscar's appearances in co-productions have been limited; most shows have their own Grouch equivalent, and Oscar only occasionally surfaces in dubbed sketches. One of the more notable exceptions is the German series Sesamstrasse, which was a straight dub of the US scenes for the first four years, and has thus continued to use Oscar sketches on a semi-regular basis through the present day.

Country/Show	Name	Performer	Picture
Denmark Leg med os fra Sesamgade and Elmo's Verden	Oscar	Max Hansen
France 1, Rue Sésame	Oscar le Grincheux	Unknown
Germany Sesamstrasse, 1973-ca.1994	Oskar der Griesgram	Gottfried Kramer
Germany Sesamstrasse, 1990s-present	Oskar der Griesgram	Michael Lott
Germany Follow That Bird	Oskar der Griesgram	Tommi Piper
Israel Shalom Sesame (Shalom Sumsum, Hebrew dub)	Mar Ashpach	Avi Pnini
Japan Sesame Street (NHK dub)	Oscar (オスカー)	Toru Okawa
Japan Sesame Street (Japan)	Oscar (オスカー)	Kawai Tomoya
Mexico Plaza Sésamo, circa 1980s	Oscar el Gruñón	Alejandro Mayen
Mexico Plaza Sésamo, 1990s-present	Oscar el Gruñón	Ricardo Mendoza
The Netherlands Sesamstraat	Oscar Mopperkont/ Oscar het Moppermonster/ Oscar de Nurks (Nurks is actually used for Grouch in Dutch)	Hans Boskamp (primarily)
The Netherlands Sesamstraat story albums	Oscar het Moppermonster	Wim T. Schippers
Spain The Adventures of Elmo in Grouchland (Catalan dub)	Oscar	Enric Isasi-Isasmendi