Many school districts face the empirical challenge of monitoring program quality to assure that all children experience pre-K environments that foster early learning and development. Factors that are exogenous to classrooms (such as evaluation timing) may play a role in estimates of program quality and yet are not fully understood. This paper examines the role of timing in pre-K classroom quality as it was observed in practice by one of the largest school districts in the United States. In the 2015-2016 school year, New York City (NYC) observed 648 of its Pre-K for All programs using the Classroom Assessment Scoring System Pre-K (CLASS), giving each program an overall average classroom quality rating at one time point. Research Findings: A series of OLS regressions indicated that CLASS scores were lower for programs observed in the fall semester in the domains of Emotional Support and Classroom Organization. Emotional Support also demonstrated a pattern of increasing scores by each month within the fall semester, providing evidence for a relationship-building period between teachers and students early in the school year. Practice or Policy: These findings may be informative for school districts and policymakers who consider using CLASS as an accountability tool.