The evolution of Le Corbusier’s architecture from cuboid, slick and white forms, and the universality of Purism in the 1920s, to an earthy roughness, undeniabl[y] inspired by Mediterranean vernacular traditions after about 1930 is well-known. For example, the Weekend House represented a very obvious tectonic shift from Villa Savoye. Since they share the same basic unit form, the unbuilt Barcelona Residential Quarter (1933) seems to be a continuation of the housing estate in Pessac (1925), the only ground-level, multi-family scheme Le Corbusier ever built. This paper argues that it represented an equally radical rethink of the principles employed in the Pessac housing scheme, but that the differences are much more subtle. The aim is to search for, and analyse the factors that mediated in the transformation of the concept from Bordeaux to Barcelona, only eight years apart. Le Corbusier was a fierce proponent of high-rise “vertical garden cities” all his life. His decision to conceptualise the Barcelona Quarter as a low-rise complex is, therefore, unexpected especially considering that CIAM (of which he was a leading member) at that time was firmly committed to highrise slabs in park-like settings. But Le Corbusier himself alluded to his intentions when he declared that he wished to create “a delightful oasis of refreshing greenery”. The word “oasis” reminds of his frequent visits to Algeria, and his observations are briefly reviewed in order to better understand the formative aspects of his experience. General layout drawings of the project were drawn on computer and these provided the data for the subsequent exploration of the urban framework and the design of the constituent dwellings. The influence of the Arab vernacular on both his urbanism and architecture became very apparent, but it seemed as if the vernacular served to enhance contextual, functional and aesthetic requirements, rather than being a dominantly formative force, as was the case at (say) Roqet-Rob in 1949.