Amidst the diverse landscape of modern educational methodologies, outcome-based education (OBE) has gained prominence as an effective approach to teaching and learning. Originating from the desire to produce specific and measurable outcomes for learners, OBE focuses on what students should know and be able to do by the end of their educational experience. Motivated by the need to delve deeper into the implementation of OBE, particularly regarding assessment preferences, this study aims to explore the types of assessments preferred by university lecturers for implementing OBE in Vietnam. Building on the existing gap in literature that emphasizes the intricacies of OBE assessment choices, utilizing qualitative research methods, in-depth interviews were conducted with 15 university lecturers from various disciplines. To analyze the gathered data, a thematic analysis approach was employed. The findings reveal a strong preference for formative assessments, aligning with educational theories such as Constructivism, Assessment for Learning (AfL), and the Cultural-Historical Activity Theory (CHAT). The study also highlights the growing adoption of project-based assessments, rubrics, and reflective practices as effective means of evaluating student outcomes. Contrary to prevailing trends, a subset of participants also advocated for well-designed standardized tests, providing a nuanced understanding of their role in OBE. Implications point to a significant shift in assessment culture within Vietnam’s higher education sector, with broader ramifications for educational policy and practice. Limitations and recommendations for further research are also discussed.