This study aimed to explore how outcome-based assessment (OBA) was adopted in an English-medium instruction (EMI) wine course at a university through design-based research (DBR). Qualitative data were collected, and analyses of the original course syllabus, two expert reviews, interviews with four students, and 14 reflection reports by the instructor were conducted. The original 15 content-oriented objectives were consolidated into six assessable intended learning outcomes integrating wine knowledge, practical skills, professional judgment, and English communication. Experiential activities, including wine tasting, label interpretation, food-and-wine pairing, and wine service, were then aligned with formative and summative assessment tasks. The findings suggest that the use of OBA helped to generate clear learning directions and ensured that experiential activities provided more meaningful assessment of professional skills. However, difficulties in implementing OBA were associated with variations in students' English proficiency and prior wine knowledge, and the increased burden of assessment work. Staged practice and scaffolding in terms of language and content were used to solve these problems. Five design principles were derived: transforming fragmented objectives into assessable outcomes; sequencing assessment from foundational learning to integrated professional performance; reducing repetitive tasks and using integrated assessments; providing differentiated scaffolding while maintaining standards; and matching the assessment criteria to each outcome. The study demonstrates that constructive alignment is not a fixed product completed before teaching but a dynamic process refined through expert reviews, classroom implementation, student feedback, assessment evidence, and instructor reflection. The findings offer practical guidance for hospitality, service-related EMI courses seeking context-sensitive assessment.