Many educational researchers across the United States have found that inquiry-based learning (IBL) supports the development of deep, meaningful content knowledge. However, integrating IBL into classroom practice has been challenging, in part because of contrasting conceptualizations and practices across educational fields. In this article, we (a) describe differing conceptions of IBL, (b) summarize our own studies of IBL in three fields of education, (c) compare and contrast the processes and purposes of IBL in our studies and fields, and (d) suggest numerous opportunities for cross-disciplinary collaborations on IBL curriculum, teaching, and research that could bolster its inclusion in K-12 education. We ground our exploration in knowledge-generating conceptualizations and practices in these fields.