Though understudied, academic structure reflects and shapes the central work--education, research, service--of higher education organizations (HEOs). Academic structure also shapes and illuminates the external environments and internal dynamics of HEOs. Despite the centrality of academic structure to HEOs and their work, our knowledge of it is limited. Research to date has primarily focused on proxies (e.g., degrees conferred) rather than academic structures themselves, and research exploring departmental and programmatic analogues often neglects the structural hierarchies in which departments and programs reside. We therefore reorient and expand on existing research to conceptualize academic structure as constituting three dimensions: horizontal (i.e., academic fields and disciplines), vertical (i.e., colleges, schools, and departments) and longitudinal (i.e., overtime behavior). Drawing on organizational theory, we use this nuanced conceptualization of academic structure to develop and evaluate expectations regarding its (1) variation across HEOs and (2) stability and/or patterns of change during a time period of environmental stress. Using latent profile analysis and original data on academic units at 115 research universities in 2012 and 2017, we estimate six distinct academic structure profiles. Our results highlight variation across universities' academic structures, as evidenced by six distinct academic structure profiles. Findings also highlight substantial overtime stability in academic structures, as well as rare differentiated patterns of change. These findings, alongside the uncommon groupings of universities allocated to profiles, suggest intriguing limits to isomorphic forces within the higher education field and warrant greater attention to academic structure in future inquiry.