Oslo String Quartet was formed in 1991 by Geir Inge Lotsberg and Per Kristian Skalstad (violins), Are Sandbakken (viola), and Øystein Sonstad (cello). It was among the 1994 prize winners of the London International String Competition, which is among the most prestigious string quartet competitions internationally. In 2007 Skalstad left the quartet in order to pursue a conducting career. Liv Hilde Klokk replaced him from the start of 2008. The quartet regularly at music festivals in Scandinavia and elsewhere, including Wigmore Hall in London and Carnegie Hall in New York. The quartet was awarded Komponistforeningens pris (the Prize of the Norwegian Association of Composers) in 1998 and the Kritikerprisen (the Norwegian Critics Prize for Music) for 1999–2000. Their CD recordings of Carl Nielsen's quartets won them a 1999 "Editor's Choice" nomination in the international journal The Gramophone, which stated "Artistically it is the finest at any price point ... totally dedicated, idiomatic performance ... full of vitality and spirit and refreshingly straightforward".

Their CD recordings include music by Edvard Grieg, David Monrad Johansen, Knut Nystedt, Klaus Egge, Fartein Valen, Johan Kvandal, Alfred Janson, Carl Nielsen, Magnar Åm, Lasse Thoresen, Ragnar Søderlind, Johan Svendsen, Jean Sibelius, Hugo Wolf, Ketil Stokkan, and Alban Berg.