Two-year-old bilingual children can show sensitivity to the language choice of their interlocutor, but do not necessarily achieve perfect separation by discourse context, e.g. speaking only French with a French interlocutor; dominance in one language is often cited as a reason for this. In this study we asked whether older bilingual preschoolers would show more absolute discourse separation than had been established with younger children because their more advanced linguistic development may diminish the constraining role of dominance in language choice. These children resided in an English majority–French minority region of Canada where virtually all francophone adults are bilingual, but not necessarily anglophone adults. Therefore, we also considered the potential interacting effects of the minority French context on children's dominance and language choice. Four French-dominant and four English-dominant bilingual children participated in two free-play situations, in French and in English. The French-dominant children showed discourse separation of the two languages in both English and French contexts, while most of the Englishdominant children spoke a lot of English in the French context. These results suggest that discourse separation of two languages by bilingual preschool children is possible, but not always practised due to the interaction of language dominance and children's sensitivity to the sociolinguistic context.