"Concept mastery skills and responsIBLe attitude skills are important skills and need to be developed for students in the Bible Studies subjects. Concept mastery skills and responsIBLe attitude skills are still relatively low based on the initial investigation. These two skills are very important for the students to have to be able to achieve Bible Studies learning objectives in Grade XI. Classroom Action Research, with 2 cycles through the stages of planning, action, observation and reflection, was implemented on 19 students at XYZ School. Each cycle was held three times. To obtain research data, the research instruments used were the observation sheets containing the assessment rubrics, student interviews, and questionnaires. The results of the research showed that there was an increase in the concept mastery skills and responsIBLe attitude skills after the cycles. The results of the percentage scores in Cycle 2, namely the concept mastery skills obtained by a percentage of the students, were 89.47%, and the responsIBLe attitude skills obtained by a percentage of the students, were 84.21% of the set success criteria, namely 70% of the students or more got a minimum score of 80. From these results, it can be concluded that the application of the Inquiry-Based Learning method can improve the concept mastery skills and responsIBLe attitude skills in the Bible Studies in Grade XI of the XYZ School. / Keterampilan penguasaan konsep dan keterampilan sikap tanggung jawab adalah keterampilan yang penting dan perlu dikembangkan bagi siswa pada mata pelajaran Bible Studies. Keterampilan penguasaan konsep dan keterampilan sikap tanggung jawab masih tergolong rendah. Kedua keterampilan ini sangat penting untuk dimiliki siswa agar mampu mencapai tujuan pembelajaran Bible Studies di Kelas XI. Penelitian Tindakan Kelas, dengan 2 Siklus melalui tahapan perencanaan, tindakan, observasi, dan refleksi, telah diterapkan pada 19 siswa Kelas XI di Sekolah XYZ. Masing-masing Siklus dilaksanakan sebanyak tiga kali pertemuan. Untuk memperoleh data penelitian, maka instrumen penelitian yang digunakan adalah data lembar observasi berisi rubrik penilaian, wawancara siswa, serta kuesioner. Hasil penelitian menunjukkan bahwa terjadi peningkatan pada keterampilan penguasaan konsep, dan keterampilan sikap tanggung jawab. Hasil nilai persentase di Siklus 2, yaitu keterampilan penguasaan konsep diperoleh persentase siswa 89.47 %, dan keterampilan sikap tanggung jawab diperoleh persentase siswa 84.21% dari kriteria keberhasilan yang ditetapkan, yaitu 70% siswa atau lebih mendapatkan nilai minimal 80. Dari hasil tersebut maka dapat disimpulkan bahwa penerapan metode pembelajaran Inquiry-Based Learning dapat meningkatkan keterampilan penguasaan konsep, dan keterampilan sikap tanggung jawab siswa pada pembelajaran Bible Studies di Kelas XI Sekolah XYZ."