We examined the relations of language skills (vocabulary, listening comprehension, and oral retell), transcription skills (spelling and handwriting fluency), and domain-general cognitions/executive functions (working memory and attentional control) to writing quality for English-Spanish emergent bilingual children in Grade 1. Data were from a convenience sample of 211 children (57% girls; 82% Hispanic, 9.5% White, 4% Asian American children) who were assessed on written composition, vocabulary, listening comprehension, oral retell, and spelling in English and Spanish; handwriting fluency and working memory in English; and attentional control rated by their teachers. Confirmatory factor analysis results showed that writing quality in English and Spanish in narrative and opinion genres was best described as a unidimensional skill. Structural equation model results showed that English oral language, English spelling, and Spanish spelling skills, but not Spanish oral language skill, were independently related to writing quality, after controlling for gender, English learner status, Hispanic status, and enrollment in dual immersion program. The relations of working memory and attentional control to writing quality were indirect, mediated by oral language and transcription skills. These results are discussed in light of theory and in the context of emergent bilingual children in primary grades.