Research on linguistic variation suggests that usage patterns are deeply embedded in native and non-native speakers' knowledge of grammar. This study explores the transfer of these variable sociolinguistic patterns at the initial stages of third language acquisition. We elicited narratives in Portuguese from two mirror-image groups of sequential Spanish-English bilingual early learners of Portuguese. Their production of variable subject pronoun expression was analysed. When comparing the two groups with regards to the linguistic factors that constrain subject pronoun expression, evidence of transfer from Spanish and not from English is consistent for both groups. We conclude that variable linguistic information is accessible in L3 transfer at beginning stages of acquisition and it is successfully predicted by holistic models of L3 acquisition.