Measuring Early Learning Quality & Outcomes (MELQO) was initiated to address needs for child development and quality of early childhood education (ECE) data, specifically for low- and middle-income countries. Drawing from existing tools, MELQO convened a consortium to create open-source tools to be adapted to national contexts, simultaneously informing global and national population-level monitoring. Beginning with the rationale and context for creating MELQO, we outline the process of creating the tools; highlight results from psychometric evaluation; and describe how the data have been used to reveal patterns of inequity and levels of learning and classroom quality. While psychometric analyses of MELQO indicate that scores should not be used to compare quality of child development between countries, country experiences suggest that data from MELQO tools within countries identify priorities for improvement of preprimary classrooms. MELQO also highlights the importance of local leadership to generate high-leverage data on ECE.