The challenges of designing group assignments in university environments, with the aim of effectively developing teamwork skills, are well documented. It is often assumed that simply placing students in assignment groups will facilitate the development of the task and interpersonal skills necessary for teamwork. However, very often students circumvent this aim by dividing the assignment up and simply assembling the resultant work together at the end. This paper examines the impact of two innovative assessment approaches on the development of teamwork skills in a one semester UX (User Experience) module in a university business school. Students elected to attend either a one-day UX Hackathon or to create a tutorial on a topic relevant to User Experience Design (UXD). Both assignments required the submission of a video as the assignment report. The groupwork skills questionnaire (GSQ) was used to assess the impact of the two assignment types on students' teamwork skills. Analysis of the results demonstrated students who attended the UX hackathon exhibited significantly improved task related teamwork skills over those who completed the tutorial assignment. Neither group exhibited an improvement in interpersonal teamwork behaviors as measured by this instrument.