As a response to the observed lack of theoretical support and generalizability of results in our current writing assessment practices, this paper proposes an alternative writing assessment design that reflects more faithfully theoretical conceptions of writing and authentic writing practices in the current information age. It starts with a brief review of existing writing theories and presents a three-dimensional model of “Information-based Academic Writing” (IBAW), which foregrounds information literacy as an integral part of the writing process and extends our current understanding and conception of the construct of writing (Yu & Zhao, 2021). The model illustrates how writing tasks situated in specific rhetorical, disciplinary, and information contexts activate one's knowledge base and generate information needs, which then guides the iterative information behaviors and writing processes, as regulated by one's affective and metacognitive strategies, to generate new knowledge and new information. Based on such a model, a conceptual framework for designing and developing a process-oriented information-based academic writing assessment is presented to show how updated writing theories may help inform and guide more authentic and meaningful assessment design. The paper ends with a discussion of the value and practical implications of such an assessment design, together with potential challenges for the developers and users of this alternative assessment approach.