This study investigates the administration of English oral assessment at tertiary institutions through the lens of Weir’s (2005) socio-cognitive framework for test validation. It focuses on three contextual dimensions — physical conditions, procedural uniformity, and test security — to examine how institutional practices influence fairness and validity in speaking assessment. Using a convergent qualitative design, data were collected from 35 teachers, 352 students, six observed test sessions, supported by testing documents from three universities in South Vietnam. Findings indicate that while direct face-to-face formats foster communicative authenticity, inconsistency in examiner behavior and test-room setup may compromise reliability. The study highlights the need for systematic examiner training, improved physical conditions, and pre-test preparation to enhance the validity of EFL oral assessment in Vietnamese higher education.