The learning journey toward sustainability requires the generation of action-oriented knowledge to understand the progress and potential adaptation of strategies to facilitate collective transformation. One integral area where advancing these strategies is essential is higher education. While efforts in the field have identified relevant learning objectives, pedagogies, and broader contributions for sustainability education to make, the sophistication of approaches to evaluating and enhancing collective learning has remained underdeveloped. This dissertation aimed to address this gap by exploring assessment in sustainability education, with the goal of supporting innovations in transdisciplinary practice by developing distinctive approaches for the field through deliberative processes that articulate design frameworks.The first study, Sustainability-Oriented Assessment, applied a formative intervention within an undergraduate course focused on professional skill development to demonstrate how a student-led rubric co-design process that drew from participative, normative, and integrative approaches contributed to student agency, expansive learning, and self-formation. The study demonstrated how students leveraged challenges and changing perspectives towards development as students and sustainability professionals. The second study, Boundary Crossings and Innovations, applied an exploratory action research approach within a community of practice of program leaders and instructors to identify barriers and possibilities for assessment practices, suggesting conceptual, practical, and logistical innovations. The strategies to enable these innovations focused on defining the field and articulating practice characteristics related to interdisciplinary approaches and transdisciplinary strategies, while meeting demands and facilitating innovations across course, program, and institutional levels. The third study, Assessment-Oriented Sustainability, applied a scoping literature review to develop a framework that integrates problem, solution, and learning orientations to sustainability by infusing educational purposes, processes, and principles to strengthen the efficacy of assessment approaches for transdisciplinary strategies. Insights from the three studies suggest that the practice of assessment plays multifaceted roles as it facilitates the design, implementation, and evaluation of sustainability endeavors. These roles include evaluative and formative functions as it appraises and advances learning, normative and deliberative functions in encouraging discussion and critical reflection, and adaptive and generative functions by indicating, motivating, and enabling dynamic learning and action for sustainability.