In this two-year ethnographic study, we explored engineering teaching and learning in fourth-grade, dual language (DL) classrooms. We discuss the biliterate disciplinary practices in these classrooms, examining data (field notes, interviews, artifacts, audio, and video recordings) gathered at a school on the US-Mexico border. Our purpose is to highlight how DL teachers collaborated to create an inquiry-based learning environment that fostered biliteracy as a resource for adding new disciplinary literacy practices. They designed experiences where their emergent bilingual students were able to leverage their existing biliterate repertoires to engage in and learn engineering design. The environment teachers promoted the development of engineering disciplinary literacies in two languages.