We apply a "tutorial design process", which has proven to be successful for a number of physics topics, to design curricular materials or "tutorials" aimed at improving student understanding of important concepts in a university-level introductory materials science and engineering course. The process involves the identification of instructional goals, the identification of specific student difficulties, the iterative design of interactive tutorials, the implementation of interactive group-work recitations, and assessment. The project, which involved over 1000 students, included extensive interviewing, testing, and iterative classroom implementation over a period of three years. Here we report on some of the identified student difficulties, several of the tutorials designed to address the difficulties, and the results of the implementation. The project has yielded 9 field-tested 48 minute tutorials in which students work together in small groups on the tutorials in the presence of teaching assistants who assess and facilitate student progress. To determine the learning outcome, we analyzed final exam scores and found that, even accounting for the fact that slightly "better" students tended to attend recitations more often, there was a significant valued-added effect of the recitations on final exam performance. These results suggest that these recitation methods and materials are effective in teaching students the difficult and important conceptual materials which they were designed to address. Furthermore, since this process was initially designed for physics courses yet is also successful for an engineering course, this implies that this process may be successful for a wide range of STEM courses.