Objectives: Parents influence a child's diet by modeling food choices, selecting the food they make available, and controlling the child's intake. Few studies have examined the covariation between parent's behavior management practices and their guidance and support for a young child's nutritional environment in early childhood. We hypothesized that parents' positive behavior support (PBS), characterized as skillful behavior management and proactive structuring of children's activities, would predict dietary quality over the course of early childhood (age 2 to 5 years), a critical period for the development of a dietary lifestyle. Methods: Participants included 731 culturally diverse, low-income families in a randomized, controlled trial of the Family Check-Up. Families participated in a yearly home visit videotaped assessment PBS and dietary quality of meals parents served to their children were assessed by coding videotapes of structured parent–child interactions. A cross-lagged panel model was used to evaluate the longitudinal relation between PBS and the dietary quality of meals served during a meal preparation task. Results: Analyses revealed that PBS repeatedly predicted meals' dietary quality the following year: age 2–3 (β = .30), age 3–4 (β = 0.14), age 4–5 (β = 0.37). Dietary quality significantly predicted PBS 1 year later: age 3–4 (β = 0.16), age 4–5 (β = 0.14). As expected, the relative strength of the relationship from PBS to dietary quality was significantly stronger than the reverse, from dietary quality to PBS. Conclusions: Positive behavior management and proactive parenting practices are an important foundation for establishing a healthy nutritional environment for young children. These findings suggest that family-centered prevention interventions for pediatric obesity may benefit from targeting PBS in service of promoting better dietary quality.