This study investigated the effect of using annotations and computer-mediated feedback to enhance learners' proficiency in English. The participants were 57 who were assigned randomly into two treatment conditions: in line (annotations and track changes), and marginal (annotations and comments) versus the control condition. Students in the treatment conditions had access to annotated vocabulary items while reading texts, and provided/received peer feedback about writing and grammar errors using track changes or marginal comments. Results showed that students in the treatment conditions significantly outperformed those in the control group on the post-tests on measures of the overall mean scores in reading comprehension, vocabulary learning, writing performance, and grammar accuracy. There was a higher significant effect for the in line location of the reading text than the marginal location on learners proficiency in reading comprehension and vocabulary learning using track changes than marginal comments on their writing performance and grammar accuracy.