Intervention studies indicate that children's childcare experiences can be leveraged to support the development of executive functioning (EF). The role of more normative childcare experiences is less clear. Increasingly, theory and empirical work suggest that individual differences in children's physiological stress systems may be associated with meaningful differences in the way they experience these early environments. Using data from a large population-based sample of predominantly low-income rural families, we tested the degree to which children's childcare experiences--quantity, quality, and type--in the first 3 years of life predicted emerging EF. Moreover, we examined whether these effects varied as a function of children's basal cortisol levels in infancy and toddlerhood--an indicator of hypothalamic pituitary adrenal (HPA) axis stress physiology. Our results showed that higher quality care predicted more effective EF at 48 months, irrespective of quantity or type. This relation did not vary as a function of children's early cortisol levels. Attending greater hours of care per week was also related to EF; however--consistent with theory--the positive association between spending more time in childcare and more positive EF extended only to children with low levels of basal cortisol at 7 or 24 months of age. Attending center-based care was unassociated with EF.