This study examined sources of variability in preschool children's positive and negative engagement with teachers, peers, and tasks, and how that variability was related to both classroom activity settings (e.g., teacher-structured time, outdoor time, transitions) and child factors (age, gender). Participants were 283 socioeconomically and linguistically diverse children drawn from 84 classrooms, 34-63 months old (M = 50.8, SD = 6.5). Each child's engagement was observed and rated multiple times within a single day. Results suggested that children's engagement varied significantly across the preschool day. Activity settings that provided children with a greater degree of choice (free choice and outdoor time) were associated with more positive engagement with peers and tasks, while teacher-structured activities were associated with more positive engagement with teachers. Transitions emerged as a difficult part of the day, associated with less positive engagement with teachers and tasks. Older children were rated higher on peer and task engagement. These findings, together with previous research, suggest that both characteristics of the classroom setting and child factors are associated with children's classroom engagement throughout a day in preschool. (Contains 3 tables.)