Heritage Spanish is often influenced by English, and previous research on late Spanish-English bilinguals suggests that their relative clause attachment preferences in Spanish are affected by English exposure. Nevertheless, recent work with heritage speakers has revealed that early (high-proficiency) Spanish-English bilinguals demonstrate a monolingual-like high-attachment preference in Spanish. Offline data from this self-paced reading study showed the same preference for bilinguals of intermediate proficiency in a meaning-oriented rather than a metalinguistic task. However, unlike in previous research, a group of late bilinguals also showed high-attachment preference, possibly because of insufficient exposure to English. Online data showed no effects for either bilingual group and a nonsignificant numerical trend toward high attachment for a monolingual group. Thus, even moderately proficient heritage speakers seem to be adept at managing interaction between two language systems, so it appears not to affect their interpretation of relative clauses.