Nutrition for school-aged children is a crucial aspect of their health. Acquired nutritional habits could persist from childhood to adulthood and school is an important environment in children nutrition. Therefore, research into the nutrition quality of foods and beverages in school canteens is of utmost importance and it has not been explored in Oman. The aim of this study was to assess compliance of foods and beverages in primary public school canteens in Muscat Governorate to the Omani Canteen Guidelines (OCG) and to assess their nutritional quality based on various international guidelines. This is a cross-sectional study of foods and beverages collected from 16 primary public schools in four districts in Muscat Governorate. Foods and beverages were collected for five days from each school canteen before or during recess time. All provided foods were collected and transported to Sultan Qaboos University (SQU) for theoretical analysis of the nutritional quality. Foods and beverages were compared to the OCG relevant lists to determine their compliance. The nutrition quality of foods and beverages was assessed based on criteria of international assessment guidelines (USDA Smart Snacks, Pan American Health Organization Nutrient Profile Model (PAHO NPM), UK Nutrient Profiling Model (UK NPM) and National Healthy School Canteen (NHSC) guidelines). Differences in compliance and nutrition quality were examined in districts, categories of food and beverage and canteen management approaches. Chi-square test of association was used to compare the difference in compliance to the OCG within independent variables. Friedman's test was used to compare the nutrition quality of foods and beverages using different international assessment guidelines collectively and with respect to their compliance to the OCG. Kruskal Wallis test was used to compare the nutrition v quality of foods and beverages between districts, categories of food and beverage and canteen management approaches. A total of 222 foods and 80 beverages were collected from 16 schools. All the beverages were compliant with the OCG while only 37% of foods were compliant. Significant differences in food compliance within districts (p < .05), food categories (p < .001) and canteen approaches (p < .05) were observed. Only 4.5%, 0% and 2% of the foods and 0%, 2.5% and 22.5% of the beverages met all criteria of nutrient quality of the USDA Smart Snacks, PAHO NPM and UK NPM, respectively. Categorizing food and beverage samples based on NHSC guidelines showed that 4.1% and 0%, respectively, were from the green category that represents the highest nutrition quality. Controlling for compliance with the OCG, there was a significant difference in nutrition quality of foods by different assessment methods (p < .001). The pairwise comparison showed difference in all pairs except the USDA Smart Snacks and the PAHO NPM in foods and in the pair PAHO NPM and UK NPM for beverages. The nutrition quality of foods and beverages was similar in all districts (p > .05). Compliance of foods to the current OCG is low and the nutrition quality of foods and beverages provided in the sampled primary public school canteens is very low when assessed by international guidelines. The nutrition quality by PAHO NPM showed similarity with other international guidelines, USDA Smart Snacks and UK NPM. Therefore, the PAHO NPM can be adapted to regulate and monitor school nutrition. These findings inform the policymakers about the status of the nutrition quality of foods and beverages in public school canteens and provide practical approaches to improve the status of school nutrition and therefore the wellbeing of the school-aged children.