In today’s networked environment, online forums emerge as a popular form of social structures that provides greater opportunities for learning from external resources without pre-established knowledge network. However, our inquiries in online forums do not always generate knowledge desideratum satisfactorily. A few recent studies noticed that communication practices become a means to characterize online forums and influences on effectiveness of collaborative learning. Our preliminary case study in an enduring online forum showed that how dialogue unfolds, i.e., asking questions and suggesting hypothetical solutions, shapes different dynamisms of collaborative learning; some dialogues are highly generative, drawing broad attention, surfacing multiple voices, and producing new knowledge through active reflection, refinement, and exploration; but some fail to be generative and display narrow, inadequate inquiry. Given the importance of dialogue and structures of interaction for learning, we propose to study how different dialogue practices in online forums are related to different levels of generative inquiry.