Previous research studies were successful in employing Task-based instruction (TBI) to enhance students' either speaking or writing skills or grammar knowledge. However, few research studies have investigated whether the TBI impacts students' grammatical performance in both speaking and writing skills. The quasi-experimental research investigated the impacts of two instructional methods between presentation, practice, production (PPP), and Task-based instructions (TBI) to see if there are any differences in improving students' productive skills. To answer the two research questions, data from the pre-test and post-test and the interviews were collected. One group was trained to learn Grammar with PPP, and the other was with TBI methods. The findings indicate that the TBI model had great impacts on students' grammatical performances in speaking and writing skills, but it was not outperformed the PPP instruction. However, the TBI model's employment was recommended to the language teachers because it created many opportunities for the students to practice the language in the grammar classrooms, and the students were motivated to get involved in the classroom activities.