Electronic learning media experience ever wider use in tertiary education as a supplement to traditional lectures, and they come in an increasing number of formats. However, we lack conclusive evidence as to which format produces the best learning outcomes, especially if we consider the vast range of possible applications. This study presents a test of three different formats - audio only, voice-over slides, and slides plus a video of the lecturer - employed in a ‘inverted classroom’ undergraduate teaching context. The results suggest that the earning effects of the video format may not warrant the additional effort required for its production, leaving voice-over slides as the preferred medium of instruction. Perhaps more importantly though, the paper provides a detailed account of the experimental set-up - which is one that many lecturers will easily be able to replicate in order to ascertain which media format is most suitable in the teaching context at hand.