The primary goal of this study is to identify intra-textual linguistic variation in university classroom talk, applying corpus-based techniques to the analysis. First, based on the automatically identified vocabulary patterns in classroom talk a large number of class sessions are segmented into smaller units of analysis. Second, the co-occurring patterns of a range of linguistic features are identified in these units applying multi-dimensional analytical techniques. Relying on these patterns, three dimensions of linguistic variation are identified in university classroom talk: (1) Contextual, directive orientation versus Conceptual, informative focus; (2) Personalized framing versus Lack of personalized framing; (3) Interactive dialogue versus Teacher monologue. Finally, taking these dimensions, session initial differences in the discourse patterns in six disciplines and three instructional levels are discussed.