Since written assignments often constitute the main form of assessment in tertiary education, academic writing skills are of paramount importance to university students. The role of academic writing in turn emphasises two aspects vital for successful written production at universities: genre awareness as students are assessed on the production of relevant genres and the use of academic vocabulary regarded as a key element of academic writing style. This study employs a corpus-based approach to explore the usage of academic vocabulary in four genres of assessed academic writing produced by multilingual foundation-level students (N=193) at a UK university. The findings show that in all writing genres there was a small set of core academic vocabulary used by the majority of students in their written assignments, accounting on average for approximately 3.6%-9% of academic vocabulary types across the genres under investigation. In addition, differences were found in the distribution and function of the core academic vocabulary items across genres. These findings have potentially important pedagogical implications for English for Academic Purposes (EAP) contexts catering for novice student writers.