This study sought to contribute to literature on college students' literacy by exploring how undergraduate disciplinary literacies are constructed and enacted within disciplinary communities. A multiple case study design was used to understand how disciplinary novice and expert members shape the meaning inherent in their literacy practices. Four disciplinary communities, each comprised of an undergraduate student with junior or senior status, a pedagogical expert, and a practitioner expert, participated in this study. Data included participant interviews, classroom observations, disciplinary literacy artifacts, shared disciplinary reading exercise and focus groups, think-aloud protocols, and literacy journals. Findings revealed that disciplinary community members constructed their understanding of disciplinary literacy through distinct sociocognitive praxes constituting disciplinary specific stances: accounting as systematic analyzers of logic; biology as critical consumers and producers of knowledge; secondary education as mindful engineers of learning; political science as critical bureaucratic agents. Participants held a tacit understanding that immersive experiences would scaffold their knowledge of disciplinary literacies. Complicating this tacit understanding, findings revealed that the development of disciplinary literacies is contingent upon the sociohistorical positioning of the discipline and its members. Implications include the need to reconceptualize disciplinary literacies beyond practices to account for the role of sociohistoric disciplinary stances. This study calls for the need for undergraduate education to respond to the reconstitutive nature of disciplinary literacies towards authentic career applications in order to more effectively nurture students' agency toward participatory membership in their disciplinary communities. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]