Modelling is an essential skill in many scientific fields, including environmental science. We designed a Modelling Competence Inventory (MCI) to measure the progress of students in acquiring competence in modelling during the bachelor curriculum. As models in environmental science borrow from many disciplines, and modelling is by nature an abstract activity that requires critical thinking, we find that designing an MCI is difficult compared to competence inventories for more physical subjects. We discuss the design process, two iterations of our MCI, and the results of testing these on a group of students before and after a modelling course. Results suggest that students understanding of the learning goals taught in the course improved somewhat, but their score on other learning goals decreased. Overall, we find that bachelor students need more supervised independent practice with modelling and building of confidence in their modelling abilities. The MCI needs further development and differentiated questions specific to the course in which the MCI is administered. The process of searching for competencies to track and developing the MCI, in cooperation with lecturers in the environmental science bachelor, by itself helped build a community of practice and led to steps to better align courses in our curriculum.