We advance theory formation in cognitive sociolinguistics by exploring the extent to which language users’ probabilistic grammar varies regionally. For this purpose, we investigate the effects of constraints that influence the choice between the two syntactic variants in the well-known dative alternation (I give Mary a book vs. I give a book to Mary) across nine post-colonial varieties of English. Using mixed-effects logistic regression and adopting a large-scale comparative perspective, we illustrate that on the one hand, stability in probabilistic grammars prevails across speakers of diverse regional and cultural backgrounds. On the other hand, traces of indigenization are found in those contexts where shifting usage frequencies in language-internal variation seem to have led to regional differences between users’ probabilistic grammar(s). Within a psycholinguistically grounded model of probabilistic grammar, we interpret these results from various explanatory perspectives, including language contact phenomena, second language acquisition, and semantic variation and change.