Discovery-based grammar teaching assumes that learners can notice forms, compare examples, and formulate rules from input, yet little is known about how such tasks unfold with low-proficiency learners in real classrooms. This descriptive qualitative study examined (1) how a Discovery Task Worksheet (DTW) on adjectives and adverbs was enacted in grammar lessons and (2) how students responded to it behaviorally and cognitively. Participants were one English teacher and 28 Grade 10 students at Al-Kautsar Boarding School, Indonesia. Data from 1 observed lesson were collected through an 18-item observation checklist, field notes, and documentation, including students completed worksheets, and were analyzed through data condensation, data display, and conclusion drawing and verification. The teacher opened with instructions and worked examples, allotted about ten minutes for individual work, and provided extensive scaffolding, partly in Indonesian. Students participated and attempted the task, but most could not yet identify patterns, compare examples, justify their answers, or write conclusions independently, and the discussion and sharing stages did not take place. Discovery in this class therefore functioned as guided, teacher-mediated discovery. The study suggests that DTW instructions, example sequencing, collaborative stages, and working time should be calibrated to learners’ proficiency, and it offers a classroom-based counterpoint to predominantly positive reports of discovery learning in Indonesian EFL contexts.