This paper explores the idea that young children's emergent literacy practices can be tools for mediating peer interaction, and that, therefore, literacy, even in its earliest stages, can support oral language development, particularly for emergent bilinguals. The paper draws on data collected during a year-long ethnographic study of 11 Nepali- and Turkish-speaking three- and four-year-olds learning English in their first year of school. Using neo-Vygotskian activity theory as a guide, this paper examines the children's classroom literacy practices, particularly around writing and the alphabet, in order to understand, first, how literacy functioned as a socially embedded activity for these students (sometimes in ways that contrasted with the official literacy practices of the classroom), and second, how that activity facilitated students' interaction across language backgrounds. Finally, this paper offers a genetic analysis, or an analysis across time, of how students' interactions with multimodal composing functioned as contexts for emergent bilinguals' oral language development, and in particular, vocabulary acquisition.