This study drew on observations of 40 secondary English language arts, history, and science lessons to describe variation in opportunities for students to engage in argumentation and possible implications for student engagement and learning. The authors focused their analysis on two broad dimensions of argumentation tasks: (1) "Instructional focus" categorized tasks as learning to argue, arguing to learn, or interactive argumentation focused on evaluating different possible meanings and interpretations of text. (2) "Inquiry space" described the degree to which the question, possible claims, and knowledge and skills needed to accomplish an argumentation task were predetermined. Findings point to task characteristics as a potentially powerful influence on instruction and resultant student engagement. Although most of the argumentation tasks focused on arguing to learn, the authors found that both arguing-to-learn and learning-to-argue tasks were frequently based on predetermined questions, answers, and content. In contrast, interactive argumentation was generally shaped by student questions and interpretations. Using contrasting illustrations from observed lessons, the authors theorize about the role of inquiry space in argumentation teaching and learning. Given that students' interactive argumentation often revealed important argumentative reasoning, the authors argue for recognizing these activities as argumentation and exploring their potential in the development of argumentation literacy skills.