While clinical outcomes in pediatric cardiac disease have improved in recent years, marked institutional and individual cardiology practice variability exists. Quality improvement science has demonstrated that reducing process variation leads to more favorable outcomes, safer practices, cost savings, and improved operating efficiency. This report describes the process undertaken to develop the first collaborative quality improvement project of the Joint Council on Congenital Heart Disease. The project chosen aims to reduce mortality and improve the quality of life of infants with hypoplastic left heart syndrome during the interstage period between discharge from the Norwood procedure and admission for the bidirectional Glenn procedure. The objective of this special article is to inform the pediatric cardiology and cardiac surgery communities of the project to help ensure that the early work by the project pilot participants will spread to clinicians caring for children with cardiovascular disease. It is anticipated that this project will add to our understanding of care for this challenging group of children with hypoplastic left heart syndrome, identifying clinical care changes with the potential to lead to improvements in outcome. It will also introduce the field of pediatric cardiology to the science of collaborative quality improvement and assist in reducing clinical process variation and improving patient outcomes across centers. Finally, it will establish an ongoing network of pediatric cardiologists and their teams linked through a longitudinal data set and collaboration for improvement and research.