The purpose of this study was to uncover sets of co-occurring, lexico-grammatical features to help to characterise successful student writing. The writing was captured by the Michigan Corpus of Upper-level Student Papers (MICUSP, 2009) and was taken from sixteen disciplines. MICUSP is a corpus of A-graded, upper-level student papers of different disciplines and paper types ( O'Donnell and Römer, 2012 ; and Römer and O'Donnell, 2011 ). Following Biber (1988) , we used a multi-dimensional analysis to identify dimensions of frequently co-occurring features that best account for cross-disciplinary variation in MICUSP. The four functional dimensions of MICUSP appear to distinguish between: (1) Involved, Academic Narrative versus Descriptive, Informational Discourse; (2) Expression of Opinions and Mental Processes; (3) Situation-Dependent, Non-Procedural Evaluation versus Procedural Discourse; and (4) Production of Possibility Statement and Argumentation. Along with a description of the methodology, this paper defines the features that constitute the factors, which have been labelled based on their communicative functions. Similarities and differences at the disciplinary and genre-specific levels are discussed as are the implications for discipline-specific and register-based pedagogies.