The authors present findings from a large 2-year study exploring the develop-ment of self-regulatory and metacognitive abilities in young children (aged 3 to 5 years) in educational naturalistic settings in the United Kingdom (English Nursery and Reception classrooms). Three levels of analysis were conducted based on observational codings of categories of metacognitive and self-regulatory behaviors. These analyses supported the view that, within the 3- to 5-year age range, there was extensive evidence of metacognitive behaviors that occurred most frequently during learning activities that were initiated by the children, involved them in working in pairs or small groups, unsupervised by adults, and that involved extensive collaboration and talk (i.e., learning contexts that might be characterized as peer-assisted learning). Relative to working individually or in groups with adult support, children in this age range working in unsupervised small groups showed more evidence of metacognitive monitoring and control. Relative to children in supervised groups, they also showed more evidence of “other” and “shared” regulation. The implications for research, theory, and educational practice are discussed.