Research Findings: The current study examined how children's parent-reported compliance at age 3 (36 months) moderated the effects of 2 dimensions of directly observed early care and education (ECE) process quality (positivity/responsivity and cognitive stimulation) during the prekindergarten year (54 months) on teacher reports of children's classroom cooperation in the fall of kindergarten. Compliance at 36 months and cooperation in kindergarten are operationalized as overt, behavioral aspects of self-regulation as appraised by parents and teachers. The sample consisted of 996 children from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development who attended formal or informal ECE settings during the prekindergarten year. Results indicated that children with low compliance at age 3 tend to demonstrate stronger cooperation skills by kindergarten when they experience more positivity/responsivity from their ECE caregivers. Main effects of positivity/responsivity and cognitive stimulation on classroom cooperation were not detected for the overall sample. Practice or Policy: The discussion addresses the importance of preparing and empowering ECE providers to help young children who enter the preschool period struggling with behavioral aspects of self-regulation, such as compliance, to improve these skills through positive and responsive caregiving.