The current study investigated the effect of an Inquiry Learning Based Program (ILBP) on EFL students' writing performance. The study followed a quasi-experimental one-group design. The participants of the study were 40 first-year EFL majors at the Faculty of Education, New Valley University during the second semester of the 2020/ 2021academic year. A writing performance pre/posttest was prepared by the researcher to measure participants' writing performance before and after the experiment. Before starting, the participants were tested on their writing performance. After conducting the experiment, they were post-tested. A paired samples t-test showed that there was a statistically significant difference between the mean score of the pretest and the posttest in favor of the posttest. This result indicated that the ILBP had a significant impact on developing EFL writing performance. It was recommended that inquiry-based learning be incorporated into EFL college writing courses.