With language characteristics shown to be a factor mediating bilinguals’ metalinguistic awareness, the present study attempts to give a clearer picture of the impact of language characteristics, avoiding confounds such as exposure opportunities and language experiences, which previous studies with comparisons made between monolinguals and bilinguals were subject to.

Two groups of bilinguals speaking the same first language (L1) but different second languages (L2s) were tested for their performance on a morphosyntactic awareness task. Other confounds (L1 proficiency and nonverbal intelligence) were statistically controlled.

After five outliers were deleted, data from 22 Chinese–English bilinguals and 20 Chinese–Southern Min bilinguals were analyzed, by mainly using analyses of covariance.

The results showed that, with nonverbal intelligence and Chinese proficiency controlled for, Chinese–English bilinguals scored significantly higher than their counterparts only on the past tense suffix task, one tested feature in which Chinese and English differ but which both Chinese and Southern Min lack. They did not, however, differ on the other contrasting feature, present suffix, probably due to its inconsistent presence in English. The two groups showed no difference on subject–object–verb and inflectional negation features that both their L1s and L2s lack.

Unlike the metalinguistic awareness measure (grammatical error detection and correction) commonly used in previous studies, our task was adapted into a version using an unlearned third language (L3) (Japanese), which could reflect children’s cross-language transfer of metalinguistic knowledge. Besides, our metamorphological awareness measure was focused on inflectional morphology, whose influence on the bilingual advantage should be important but has yet received scant attention in the earlier literature.

The overall results cross-validated the important role of language characteristics in bilinguals’ development of metalinguistic awareness and suggested that the metamorphological awareness is likely to facilitate bilinguals’ learning of an L3.