In a foreign language context, grammar is always construed as an indispensable element to learn. It is the question of how to learn it that becomes a key issue to examine. Concern is placed on how grammar instructions can nurture and develop students' grammar interlanguage system. A wave of research ranging from intensive treatment toward specific linguistic features to focus on form in interactions is put forth. Apart from the insightful research on grammar, some teachers still have a propensity to rely on language input through the adoption of meaning-oriented tasks. A common view held by teachers is that an abundant exposure to language use would warrant the development of students' grammar. The communicativeness of the tasks is believed to enable the grammar learning to take care of itself. While the view, to a large degree, is justified, it might not be sufficient for the whole processing of the intricate development of L2 grammar learning to occur. Accordingly, Swain (1994) sheds light on roles of output as potential learning mechanisms to facilitate the process. This study is an attempt to find some evidence of roles of output in L2 grammar learning.