In this study, two pedagogical aspects occurred within the results. One is the perspective of ESL teacher training for teaching relative clauses; the other is the consideration of learning styles of Taiwanese ESL learners in an online classroom environment. These two perspectives will be explained in the following paragraphs in terms of the study of teachers' cognitions.The first perspective of the findings of this pioneering study, which sheds light on teaching relative clauses by corpus-based materials, discovered several implications for ESL English grammar teacher training. The first implication is that ESL teacher training courses should not take for granted that in-service English teachers will have acquired abilities to teach grammar using corpus-based materials. The results of this study found that the teacher participants tended to avoid applying DDL into their teaching. One of the possible reasons, as previous research has illustrated, is whether the native and non-native English teachers were discovered to have inadequate linguistic and grammatical awareness abilities, thereby affecting their teaching methodologies in the provision of appropriate linguistic input for their students (Andrews, 1999b, 2001, 2003b; Borg, 2001). This also implied that English teachers require a wide range of specific linguistics and educational training practices regarding how to utilize corpus-based materials in their English teaching. Hence, teachers' cognitions could be upgraded and enhanced in order to adjust to efficient teaching using DDL and corpus-based materials.