Contributing to more sustainable diets is a major challenge for contemporary environmental education. It implies an increase in the share of plant-based foods and of home-cooked meals. Awareness of this is widespread but taking concrete action is not easy. What competences does it call for? To identify them, we proposed an 8-month training course to groups of young adults in France. Their consumption of vegetables and the competences they mobilized were collected at the end of the training and 8 months later. The competences used by the participants with the lowest consumption of vegetables included controlling their food budget, collecting information about processed foods and planning what they would like to eat. The competences used by the participants with the highest consumption included planning meal preparation, being flexible, choosing quality products and mastering the preparation of fresh vegetables. These results are of interest for designing education programmes for sustainable diets.