Background: Previous studies of mastery motivational climates within physical education have reported that providing students with opportunities to become self-directed leads to a number of positive outcomes, including skill attainment and increased perceptions of ability. Nonetheless, within all of these studies, there has been no account of the teaching/learning process or the behaviour of the students and teachers within the various interventions. Purpose: The purpose of this study was to provide a micro-analysis of life in a mastery climate which was grounded in the classroom ecology paradigm. Participants and setting: The participants in this study were 13 children (11 boys and 2 girls) all aged 4 years at the commencement of the programme. The children were attendees at a day-care centre that serves mostly African-American children from the local community who are environmentally at risk for developmental delay and poor health. The teacher in this study was a faculty member at the university where the programme took place. For 30 minutes each Tuesday and Thursday, the children participated in a programme of motor skill instruction that was based upon the key principles of a mastery-motivational climate. Selected station activities were designed to promote the acquisition of locomotor and object control skills. Methods: A mixed-methods approach was taken, with data sources including interviews with the teacher, and an analysis of the ecology of the gymnasium using a modified version of the task structure system. Focus was placed upon the task goals, the teacher's accountability strategies, as well as task accomplishment in both the managerial and instructional task systems. Findings: The key finding from this study was an appreciation of how time is a significant factor in the ways in which children initially responded to and eventually embraced the freedoms afforded to them in a mastery climate. Of particular note, the results show substantial differences in the children's lesson engagement not only across time, but also within lessons themselves. It is hypothesized that as they progressed through the programme, the children not only were more able to identify the demands of the task but were also able to filter out extraneous signals that might promote off-task or inappropriate behaviour. Conclusions: The design of this study reinforced the value of adopting an ecological analysis of life in a mastery climate. Further, the results of the study showed the value of examining young children's engagement over a lengthy intervention. While such climates are expected to have lower levels of engagement and higher levels of off-task behaviour than more teacher-directed formats, by the end of the study the children were able to achieve levels of appropriate task engagement above 80% of lesson time.