The mounting numbers of young Hispanic children in the United States (now about 25% of those under five) require unique considerations in efforts to meet their particular needs for preschool education. Among the most agreed upon practices to address these needs are the provision of strategic and intentional interactions in English with use of children’s home languages (HLs) for instruction. However, challenges include the capacity among the workforce to deliver instruction in two languages and whether assistant teachers may be relied on to provide HL instruction. Further, to assess the quality of interactions deemed best for dual language learners (DLLs) use of an observation tool explicitly designed to understand these contexts for DLLs is warranted. The purpose of this study was to examine the relative effectiveness of different teacher and assistant teacher bilingualism combinations on teaching practices as assessed using the Classroom Assessment of Supports for Emergent Bilingual Acquisition (CASEBA; Freedson, Figueras, & Frede, 2009), a tool specifically designed for measuring language supports for preschool DLLs. Results indicate that classroom quality scores relative to staff language configurations differed with Spanish-speaking lead teacher pairs, earning significantly higher scores than the other staff language configuration groups. Associations between the CASEBA and children’s English and Spanish receptive vocabulary scores were also examined, revealing a relationship between assistant teacher’s home language use and English receptive vocabulary scores. These findings present a springboard for policy conversations regarding the supply and demand of bilingual teachers and teacher assistants, preservice training and professional development, and the ways in which a specific classroom observation tool can inform all of these areas. (author abstract)