When reading, words are broken down into morphological components that involve meaning and letter-order information; These are activated in two languages in bilinguals. These dual representations facilitate reading in bilinguals proficient in both languages, with efficient cross-language activation and morphological processing. This dual activation may be detrimental in bilinguals with low-to-intermediate second-language (L2) proficiency, as overlap and interactions between strong- and weak-language representations of morphological components may inhibit lexical access. This study investigated how dual-language representation impacts access to morphological information during reading, and whether bilingual proficiency can mediate effects. Grade 6 monolingual (N = 26), high-proficient (HP; N = 11) and low-proficient (LP; N = 9) bilingual children participated. Standardized reading and L2 vocabulary measures were followed by a primed lexical decision task in English. Prime-target pairs were semantically related (e.g., walker-WALK), orthographically related (e.g., corner-CORN), or unrelated. Event related potential (ERP) and response time (RT) data were analyzed, focusing on how strength of dual language proficiency can impact reading in bilinguals. Comparisons between bilinguals and monolinguals were also examined. RTs and ERP N400 waveforms involving semantic processing were facilitated by semantically related primes for monolinguals. LP bilinguals performed like HP bilinguals, but with ERP N250 orthographic-prime facilitation. HP bilinguals relied more on orthographic information, with reduced primacy of semantic information in word identification. Results support interactive activation accounts of bilingualism, demonstrating that morpho-syntactic and -orthographic activation presents differently in bilinguals of varying L2 proficiency and in monolinguals; possibly driven by the quality of dual language representations.