This study compares the effects of using online corpus and online dictionary as Data-Driven Learning (DDL) on EFL students' grammar mastery and their perceptions after learning with the two media in grammar instruction. The experiment with a counterbalanced design was employed with two replications, and 65 students in two intact classes participated. In the first replication, 33 students of the first group learned grammar with an online corpus, while 32 students of the second group learned using an online dictionary. In the second replication, the first group of students learned grammar with an online dictionary, while the second group learned with an online corpus. After each replication, the students took a grammar test and filled in a questionnaire. The grammar tests after learning with an online corpus were compared to the results of the grammar tests after learning with an online dictionary. Then the students' responses on both media were also compared. The statistical evidence comparing grammar test results reveals no statistical difference in students' grammar mastery after learning with an online corpus and an online dictionary. The same result is obtained when comparing their perceptions after learning with both media.