Collaborative teaching models serving secondary multilingual learners designated as English Learners (ELs) have become increasingly prominent but remain understudied. This study draws upon an ecological framework and uses quantitative and qualitative survey findings from a national sample of school districts in the United States to investigate the prevalence and use of collaborative practices. The study examines variations in how collaborative models are structured and implemented, as well as how they vary by district characteristics. Findings suggest that collaborative practices are present in many types of districts but are typically more common in larger, urban districts with higher percentages of EL-designated students. Collaborative practices are more prevalent at middle school (grades 6-8) than high school (grades 9-12) levels but tend to occur across multiple key content areas. In relation to coteaching in particular, findings align with previous research on inequitable status and teaching responsibilities faced by some ESL teachers. District supports for collaboration vary, with professional development more prominent than teacher release time for collaborative planning. Overall, findings indicate that district resources and instructional capacity play important roles in the implementation of collaborative practices, and organizational capacity may influence the status of ESL teachers in these models.