Background: To enhance the impact of school nutrition programs on children's health, more information is needed on the associations between healthy and unhealthy food offerings during school lunch periods and children's eating behavior. The purpose of this study is to evaluate the contributions of food offerings and participation in school lunch programs on children's overall (both in- and out-of-school) eating behavior. Methods: A cross-sectional observational study was conducted in which 2039 students in 12 elementary and 10 middle schools reported their eating behavior and the frequencies with which they purchased meals and a la carte items in the school cafeteria. Food service managers from each school provided information on the availability of foods and beverages during school lunch periods. Multilevel regression analyses were conducted to identify school- and student-level predictors of children's eating behavior. Results: The availability of nutritious foods during school lunch periods was associated with healthier eating behavior among students. However, this effect was observed only among children who infrequently purchased a la carte food items, and not among those who were frequent purchasers. Conclusion: Increased availability of fruits, vegetables, whole grains, and low-fat dairy products as components of school meals may be an effective strategy to promote healthy eating behaviors among children. Improving the nutrition standards for foods offered in competition with federally reimbursable school meals may enhance the positive effects of school meal programs on student eating behavior. (Contains 1 figure and 2 tables.)