Young children and their families benefit from early care and education (ECE) settings that implement high-quality practices that support children's well-being, health, and safety. Activities to support quality are a focal point of federal and state investments, including more than $1 billion of the Child Care and Development Fund and nearly $240 million in Head Start Training and Technical Assistance. The work of quality improvement in ECE is challenging using existing methods, and sustained changes in quality across ECE settings have not been widespread. ECE leaders and staff are seeking new approaches to quality improvement that can promote meaningful and sustained changes in practice. The purpose of this brief is to share findings from the Culture of Continuous Learning (CCL) project, a study of the Breakthrough Series Collaborative (BSC) in ECE programs. The BSC is a quality improvement methodology tested in ECE programs to support practice change by addressing individual and organizational factors associated with sustaining high-quality practices. This brief will provide information for decision makers at the federal, state, and local levels who fund quality improvement strategies. [This brief was prepared with University of Massachusetts Boston, Institute for Early Education Leadership and Innovation and JRA Consulting Ltd. For "Promoting a Culture of Continuous Learning in Early Care and Education Settings. OPRE Report 2021-208," see ED616411.]