The current study aimed at using curriculum-based measurements (CBM) to identify reading disabilities in oral reading fluency and reading comprehension in third and fourth grades of Cycle one of basic education in Muscat, the capital and largest city of Oman. Additionally, the study aimed at identifying the cut off scores in students? performance on oral reading fluency and reading comprehension CBM in order to screen for reading disabilities. To achieve this aim, three equivalent forms of curriculum- based measurements in the areas of oral reading fluency and reading comprehension were administered twice at the beginning and in the middle of the academic year to third and fourth graders in both public and private schools in Muscat. Participants included 412 students from third and fourth grades. Results showed that the cut off score was 48 words per minute in oral reading fluency for fourth grade students and 27 words for third grade students. Results also showed that the cut off score on reading comprehension maze CBM was 13 correct responses for fourth grade students and 7 correct responses for third grades students. The ROC curve analysis provided evidence that the CBM had a sensitivity of .80 and that there were no statistically significant gender differences between public and private schools. in in three minutes for fourth grades students