This qualitative study investigates tutor and student interaction in an online multiliteracy center (the Hub) at a major public research university. This study addresses a gap in the current literature on how writing centers transition to multiliteracy centers and prepare their tutors for consulting with students around aspects of design. There is also a lack of knowledge concerning the digital tools and mediating practices that people engage in during online tutoring sessions. At the Hub, tutors and students met through a video call and within the shared composing medium Google Slides; the environment was synchronous and multimodal. Participants included two tutors and eight students. The conceptual framework focuses on a sociocultural view of learning that brought together key tenets from writing center scholarship, multimodality theory, and Vygotsky's (1978) notion of the Zone of Proximal Development (ZPD) as the space where learning occurs. The main research question of this study was as follows: What is the nature of the interactive processes of students and tutors, as situated in an online multiliteracy center and mediated by digital tools and modes? Data included screencast recordings of entire sessions and pre- and post-session report forms filled out by tutors and students. I analyzed data through coding session transcriptions of both talk and other simultaneous modal interaction, then writing qualitative session summaries to reveal salient patterns across sessions. The main findings were as follows: 1) the student and tutor talk within the online Hub provided the modal foundation to the learning interaction process; 2) the social, multimodal exchange within the digital Hub online tutoring environment offered affordances and constraints; and 3) the Hub virtual conferencing environment supported the embedding of customized mini-lessons using the product as the context for learning. As a result of this study, there are implications for practice regarding the role of the multiliteracy center at the institution and the training of tutors for such services. Implications for further research include the opportunity to investigate how learning occurs in online environments and how educational research strategies must remain agile in a continually shifting 21st century technological landscape. [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.]