For decades, research on the quality of early care and education has helped identify features of those settings that play some role in promoting children's learning and development. We offer this brief commentary as a framework for considering not only the topic and papers in this special issue, but more importantly, as a motivating heuristic for next generation of research and development on the assessment and improvement of measuring quality. First, we present some observations on the contemporary debates about quality, including a discussion of effect sizes, causality, conducting horse race analyses, and bringing measures to scale. We then argue that making progress towards measuring quality requires the field to think carefully about the focus of assessment, tradeoffs between reliability and validity, the diversity of the classroom and teachers, and scientific and technical advances. Absent these considerations, individually and in terms of their integrative links, discussions or presentations of new and improved measures of quality will not help advance the understanding and appropriate use of such instruments. (author abstract)