Dissertations are a challenging requirement for completion of a doctoral program, especially for multilingual students pursuing a degree in a second language medium of instruction, as is the case for many international students pursuing degrees in the United States. Although institutions provide various means of support for graduate students, including English instruction for non-native speakers, Ph.D. students report difficulty achieving program requirements. The doctoral dissertation has been recognized as a major hurdle to program completion, due to the complex variety of skills it draws on. This study considers how genre-based writing instruction GBWI delivered through individual writing tutoring might help doctoral students address these multifarious challenges. It is situated in the field of English for Academic Purposes (EAP), which is concerned with the communicative needs of multilingual learners. EAP research on GBWI has shown its effectiveness in classroom instruction, but it has not been investigated in other pedagogical contexts. Individualized peer tutoring, such as that provided in graduate writing centers, holds promise as a context in which GBWI could be adapted for supporting multilingual dissertation writers. However, currently there are no comprehensive descriptions of GBWI in tutoring, and graduate students' uptake of tutoring pedagogy has not been extensively examined. The purpose of this study is to 1) establish a comprehensive description of GBWI tutoring in a GWC-like context, and 2) to explore how the practices enacted during such tutoring are reified in tutoring sessions and in non-native English speaker doctoral students' dissertation writing. This two-part study begins with a comprehensive description of peer writing tutoring practices in the Center for Communication Excellence (CCE) at Iowa State University, which provides communication skill development support to graduate students and postdocs. This description is used to analyze four case studies comprised of a non-native speaker dissertation writer and a CCE tutor. Using data from tutoring sessions, interviews, and dissertation drafts, connections are traced from tutoring practices to student uptake and reification in students' writing. This study contributes a model for providing GBWI through graduate writing tutoring and evidence of reification of genre-based writing instruction in a graduate writing center. It also contributes, as a methodological resource, a relational definition of writing quality that captures the nature and ethical stance of quality judgments rendered in this dissertations analyses, as well as an analytic framework compatible with this definition of writing quality. This research has value for expanding applications of GBWI in novel contexts. It also has practical implications for institutions developing broader support for doctoral students and practitioners considering how to target feedback to dissertation writers. [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/en-US/products/dissertations/individuals.shtml.]