Several strands of research in applied linguistics have increasingly focused their attention on the application of genre theory to the classroom. In advanced academics, the genres of disciplinary communities serve gate-keeping functions that students must negotiate in order to succeed in their academic endeavors. Often without explicit instruction, students must learn to master the stylistic, rhetorical, and organizational conventions of their disciplinary communities. This problem is confounded by occluded genres--genres whose exemplars are private or confidential, and thus cannot be readily used as models. This study examines one specific occluded academic genre--the MBA Thought Essay. This study found the genre shares features in common with academic discourse and popular business management literature, but is also characterized by a high degree of structural and linguistic variation. Because the genre is occluded, authors cannot fashion their discourse on prototypical texts; rather, they appear to rely upon other genres to structure their texts. The present study presents a complex picture of occluded genres involving a number of interrelated factors: degree of occlusion, genre maturity, structural and lexico-grammatical variation, and discourse community socialization and turnover.