This paper introduces a new resource designed to facilitate the quantitative investigation of syntactic variation in spoken language from a comparative perspective. The datasets comprise homogeneously annotated collections of "interchangeable" (i.e. competing) genitive and dative variants in four varieties of English: American English, British English, Canadian English, and New Zealand English. To showcase the empirical potential of the data source, we present a suggestive analysis that investigates the extent to which the probabilistic grammar of genitive and dative variant choice differs across varieties. The statistical analysis reveals that while there are a number of subtle probabilistic contrasts between the regional varieties under study, there is overall a striking degree of cross-varietal homogeneity. We conclude by outlining directions for future research.