Online collaboration exercises were used as part of a diverse assessment package for an undergraduate differential equations course. Online collaboration served as a highly effective method for promoting and assessing generic graduate capabilities such as writing in a context-relevant manner and the development of self-awareness with regard to mathematical strengths and limitations. We present a number of examples of collaborations which can be broadly classified as "illustrative" or "corrective" in nature. The assessment strategy was found to be valid and largely reliable, although a number of issues arose with regard to reliability of peer-provided, formative feedback. These issues are addressed and suggestions for overcoming them are presented. Finally, a discussion of the successes of the strategy is presented along with a number of examples of positive outcomes resulting from the use of online collaboration as a learning activity.