Adults and children learning a second language show difficulty accessing expressive vocabulary that appears accessible receptively in their first language (L1). We call this discrepancy the receptive–expressive gap. Kindergarten Spanish (L1) – English (L2) sequential bilinguals were given standardized tests of receptive and expressive vocabulary in both Spanish and English. We found a small receptive–expressive gap in English but a large receptive–expressive gap in Spanish. We categorized children as having had high or low levels of English exposure based on demographic variables and found that the receptive–expressive gap persisted across both levels of English exposure. Regression analyses revealed that variables predicting both receptive and expressive vocabulary scores failed to predict the receptive–expressive gap. The results suggest that the onset of the receptive–expressive gap in L1 may have been abrupt. We discuss possible mechanisms underlying the phenomenon.