A recent model of sound change posits that the direction of change is determined, at least in part, by the distribution of variation within speech communities. We explore this model in the context of bilingual speech, asking whether the less variable language constrains phonetic variation in the more variable language, using a corpus of spontaneous speech from early Cantonese-English bilinguals. As predicted, given the phonetic distributions of stop obstruents in Cantonese compared with English, intervocalic English /b d g/ were produced with less voicing for Cantonese-English bilinguals and word-final English /t k/ were more likely to be unreleased compared with spontaneous speech from two monolingual English control corpora. Whereas voicing initial obstruents can be gradient in Cantonese, the release of final obstruents is prohibited. Neither Cantonese-English bilingual initial voicing nor word-final stop release patterns were significantly impacted by language mode. These results provide evidence that the phonetic variation in crosslinguistically linked categories in bilingual speech is shaped by the distribution of phonetic variation within each language, thus suggesting a mechanistic account for why some segments are more susceptible to cross-language influence than others.