Objective: School summer holiday clubs in deprived areas of Wales were evaluated to examine opportunities for healthy eating and physical activity and explore delivery processes. Methods: Ten Food and Fun clubs participated in 2016. Quantitative data (child and parent surveys; N = 196, N = 84) assessed the opportunity to provide children with breakfast and lunch. A sub-sample of children wore an accelerometer (N = 41) to evaluate the opportunity for achieving 1-hour of moderate to vigorous activity (MVPA) at club. Features of successful club delivery were identified through; focus groups (child and parent; N = 74, N = 69) and interviews (staff/volunteer; N = 32). Results: Opportunities for healthy eating were delivered with high fidelity: 86% of children reported breakfast consumption and 75% eating a healthy lunch. On club days, children reported consuming fewer sugary snacks (66%), fewer sugary drinks (81%), and more fruits and vegetables (67%). About 71% of children achieved the recommended MVPA at club, with children engaging in more MVPA (+17 minutes/day, p < 0.01) on average compared to non-club days. Successful delivery processes were: use of school facilities and staff; flexible partnership-working; and whole family involvement. Conclusions: Schools appear to provide a suitable setting for the delivery of healthy eating and physical activity opportunities during school summer holidays.