The purpose of this study was to examine the effect of using Curriculum-Based Measurement (CBM) on the learnersâ achievement in L2 grammar and reading in an EFL context and to further investigate whether the studentsâ classroom performances would predict their final exam results. To conduct this study, two classes, each containing 30 female students, were selected among the existing 1st grade high school classes in a high school. Prior to the treatment, all participants were given both reading and grammar tests so as to make sure of any initial differences among them. CBM was randomly implemented in one of these classes (as an experimental group) once a week over a 12-week period to monitor their progress in reading and grammar. At the end of the treatment, all participants took the achievement test. The results of two independent-samples t-tests indicated that CBM significantly improved studentsâ L2 reading and grammar achievement during the term. Also, the results of two linear correlations revealed that CBM outcomes during a semester significantly predicted final exam results.