Monthly menu planning in mass catering is a complex decision problem with many objectives, constraints and factors like healthy eating, limited budget, seasonality effects, capability of producing food for thousands of people within a limited time, customer satisfaction, interactions between periods of planned meals, harmony of meals which are served together, preparation constraints etc. In the scientific literature, there is no serious study which simultaneously considers all of the aforementioned factors simultaneously within a decision support framework. In practice, menu planning studies are usually based on information gathered from experts and previous practices. Due to lack of a systematic procedure it is almost impossible to satisfy most of the objectives and constraints. In the present work, first time in the literature an integrated decision support system is designed which considers many operational and practical constraints and objectives simultaneously. A real life application of the proposed decision support system is also carried out at DEU Canteen-Cafeterias Department with real data for model verification and validation.