<![CDATA[Passive voice remains one of the most challenging grammatical structures for Indonesian EFL learners, largely due to structural differences between English and Indonesian sentence systems, particularly in tense marking and participant perspective. This study aims to identify the types of errors made by Indonesian EFL students in constructing passive voice sentences and to explain these errors from the perspective of Cognitive Grammar. The study employed a descriptive qualitative design supported by quantitative data. Participants were fifth-semester students of the English Department at STBA JIA Bekasi, selected through purposive sampling. Data were collected through a 20-item passive voice transformation test and analyzed using the Surface Strategy Taxonomy proposed by Dulay, Burt, and Krashen (1982), while learners' conceptualization was interpreted through Langacker's (2008) Cognitive Grammar framework. The findings revealed 224 errors, with misformation as the most frequent category, accounting for 83.9% of all errors and encompassing inappropriate use of tense (37.1%), verb form errors (26.3%), inappropriate use of auxiliary verbs (13.4%), and inappropriate verb use (7.1%). This was followed by omission errors (8.9%, comprising omission of auxiliary verbs and omission of letters) and misordering errors (7.1%). From the Cognitive Grammar perspective, these errors reflect difficulties in temporal grounding, participant profiling, and event construal. The findings suggest that students face challenges not only in applying grammatical rules but also in conceptualizing passive constructions appropriately.]]>
