Accurate, reliable, and scalable measurement of classroom quality represent a critical tool for ensuring that young children benefit from early learning programs. The Early Childhood Classroom Observation (ECCO) study was designed to better understand how video recordings can support high-quality measurement of pre-kindergarten (pre-K) classrooms, using two common measures of early learning programs: Classroom Assessment Scoring System (CLASS) and Early Childhood Environmental Rating Scale, 3rd Edition (ECERS-3). For each measure, the study team compared the reliability of observations gathered through video and live (in-person) classroom observations. The team also interviewed teachers and program leaders to understand their perceptions of the challenges and benefits of video observations. The study team conducted live and video scoring of 160 observations of pre-K classrooms, conducted surveys of nearly 60 teachers, and interviews with 17 teachers and program leaders. In general, the authors find that pre-K classroom observations can reliably be conducted over video and that video scores are generally comparable to live scores. There are some differences between live and video scores that may limit comparability for certain classrooms, different aspects of practice observed, and the purpose of the observation.