Background: The Children’s Oncology Group (COG) is the only organization within the National Cancer Institute’s National Clinical Trials Network dedicated exclusively to pediatric cancer research. The purpose of this article is to provide an overview of COG’s organizational structure, to characterize its institutional and individual membership, and to summarize enrollments onto COG clinical trials. Method: Data from 2013 to 2015 were compiled from sources internal (Network Operations, Statistics and Data Center, Chair’s Office) and external (American Hospital Association, American Nurses Credentialing Center) to COG, to present a comprehensive overview of COG’s structure, individual and institutional membership, and group operations. Results: In 2016, COG comprised 8,785 individuals from 223 member institutions, across seven countries. An average of 9,661 new patients were registered with COG per year over the most recent (2013-2015) 3-year period. Over the same 3-year time frame, there were an average of 16,836 enrollments onto therapeutic (i.e., treatment) and nontherapeutic (e.g., epidemiology, survivorship, biology) trials per year. Conclusions: COG institutions have diverse characteristics related to size, geographical location, and infrastructure. Individual membership also reflects diversity with representation from over 28 disciplines and groups. The diversity of COG institutions and individual members allows for unique perspectives and contributions to science unified under a common goal to enroll children/adolescents onto clinical trials. COG’s collaborative, multidisciplinary approach to science functions to support the development of research that seeks to continually improve outcomes for children and adolescents with cancer.