The present study examined how the dosage and quality of the federal preschool program “Head Start” (HS) in the US related to children’s self-regulation skills in kindergarten. Using Propensity Score Matching and multiple regression (OLS), this study explored how the number of years and hours a week of HS were related to self-regulation among 2,383 children, who entered the program either at 3 or 4 years old. An additional year in HS was significantly positively associated with self-regulation in kindergarten, while the number of hours a week in HS was not. However, the quality of teacher–child interactions moderated the relation between hours a week in HS and self-regulation. Findings contribute to the growing body of evidence about how dosage and quality of early childhood education experiences relate to children’s development. (author abstract)