This quasi-experimental study investigated the effects of input-enhancement and production of sentences, containing the target structures, on learning grammar by Iranian Intermediate EFL learners. Sixty male students in three input, output, and control groups participated in the study. After checking the homogeneity of the participants with a proficiency test, the researchers administered a pretest. Input-based group received input enhancement within reading texts in which the target structures were highlighted with different techniques such as bolding and underlying. The output-based group were required to produce some sentences including target structures based on reading texts. The control group received traditional grammar instruction. The results of ANCOVA revealed that both experimental groups learned the target structures better than the control group; however, the input-based group outperformed output-based group in learning target grammatical structures. The findings of the study suggest the widespread use of input-enhancement, as one of the techniques of focus on form, plays a significant role in enhancing grammatical accuracy.