As part of Phase 3 of the Universal Preschool Child Outcomes Study (UPCOS-3), Mathematica Policy Research worked with the First 5 LA Children and Families Commission and Los Angeles Universal Preschool (LAUP) to conduct a descriptive study of the characteristics of classrooms in LAUP programs during winter 2010. This study has a particular focus on the specific instructional practices used to support English language learners (ELLs) in LAUP's center-based and family child care programs. The study includes two key components: (1) classroom observations using measures determined as appropriate for settings with children who have diverse language backgrounds and (2) a survey of teachers regarding the instructional practices they use with children who are ELLs. The author reviews the procedures underlying the selection of classroom observation measures, the development of the instructional practices questionnaire, and the sampling procedures used for each type of data collection. They discuss the results from data collection using the classroom observation measures (Chapters II through IV) and instructional practices questionnaires (Chapter V) and they examine the relationships among these measures and summarize across them. (Contains 171 tables, 13 figures and 27 footnotes.)