Bilingual children often lag behind monolinguals on standardized measures of language acquisition, such as vocabulary tests. This bilingual lag could be related bilinguals' lesser experience with the target language relative to monolinguals. In this study, we predicted that sequential Mandarin-English bilinguals would perform worse than same-aged English monolinguals on a standardized measure of complex sentence production. As predicted, the bilingual preschoolers performed worse than age-matched English monolinguals. However, once English experience was covaried, there was no significant difference between the two groups. After controlling for age, we tested three predictors of complex sentence production: (1) English vocabulary, (2) verbal memory, and (for the bilinguals) (3) Mandarin vocabulary. For both bilinguals and monolinguals, English vocabulary and verbal memory were significant predictors. These results support the argument that experience with a particular language is highly predictive of children's ability to produce complex sentences in that language. Verbal memory is also an important predictor of individual differences in the ability to produce complex sentences.