Community-based policy, systems, and environmental interventions have the potential to reduce modifiable risk factors for obesity early in life. The purpose of this scoping review was to characterize the breadth, generalizability, and methodological quality of community-based diet and obesity-related policy, system, and environmental interventions during the first 1000 days of life, from pregnancy to 24 months of age. Eight databases were searched, and 83 studies (122 references) were included. Data were extracted for breadth (intervention characteristics), generalizability (reach, effectiveness, adoption, implementation, and maintenance), and study quality (Downs and Black Checklist). Systems and environmental approaches were common (> 80%), relative to policy approaches (39%). The majority (60–69%) occurred in the prenatal period and early infancy (0–3 months), assessed breastfeeding or child growth/obesity (53% for both), and included people with lower income (80%) or racial and/or ethnic minority groups (63%). Many interventions reported positive outcomes (i.e., in the expected direction) for child diet, breastfeeding, and feeding practices (> 62%). Few reported intervention maintenance or spanned the full 1000 days. Most studies were classified as good (32%) or fair (56%) methodological quality. The interventions mainly addressed pregnancy and early infancy. Rigorous and representative investigation is needed to improve intervention reach, sustainability, and application in toddlerhood.