School nutrition policies limiting access to sweetened beverages, candy, and salty snacks have the potential to improve the health of children. To effectively evaluate policy success, appropriate and validated dietary assessment instruments are needed. The objective of this study was to develop and validate a beverage and snack questionnaire suitable for use among young adolescents. A new 19-item Beverage and Snack Questionnaire (BSQ) was administered to middle school students on two occasions, 2 weeks apart, to measure test–retest reliability. The questionnaire inquired about frequency of consumption, both at school and away from school, of soft drinks, salty snacks, sweets, milk, and fruits and vegetables. Students also completed 4-day food records. To assess validity, food-record data were compared with BSQ data. Forty-six students of diverse backgrounds from metropolitan Seattle, WA, participated in this study. Participants answered the BSQ during class time and completed the food record at home. Pearson correlation coefficients assessed test–retest reliability and validity. Using frequency per week data, the test–retest reliability coefficients were r=0.85 for fruits and vegetables consumed at school and r=0.74 and r=0.72 for beverages and sweets/snacks, respectively, consumed at school. Correlations ranged from r=0.73 to 0.77 for foods consumed outside of school. Compared with the criterion food record, validity coefficients were very good: r=0.69 to 0.71 for foods consumed at school and r=0.63 to 0.70 for foods consumed away from school. The validity coefficients for the 19 individual food items ranged from r=0.56 to 0.87. This easy-to-administer 19-item questionnaire captures data on sugar-sweetened beverages, salty snacks, sweets, milk, and fruit and vegetables as well as a more lengthy and expensive food record does. The BSQ can be used by nutrition researchers and practitioners to accurately evaluate student consumption of foods that are the focus of school nutrition policies.