In bilingual children, more so than in monolingual children, comprehension abilities exceed production abilities. While this receptive-expressive gap in bilinguals has been well documented, little is known about its development. The present study tracked growth in the Spanish and English receptive and expressive vocabularies of 52 bilingual children from 4.5-10 years. The children's English vocabularies grew faster than their Spanish vocabularies, more so in the expressive domain than the receptive domain. The proportion of children who were English-dominant also increased more in the expressive than the receptive domain. By age 10, the children's expressive skills were almost always English dominant while their receptive skills were most frequently balanced. Among children who hear a heritage language at home and a societal language at school, trajectories of dual language development differs in the expressive and receptive domains. These longitudinal data suggest continuity between the receptive-expressive gap observed in bilingual children and the receptive bilingualism often observed in adults.