In the United States, school curricula are often created and taught with distinct boundaries between disciplines. This division between curricular areas may serve as a hindrance to students' long-term learning and their ability to generalize. In contrast, cross-curricular pedagogy provides a way for students to think beyond the classroom walls and make important connections across disciplines. The purpose of this paper is a theoretical reflection on our use of Expansive Framing in our design of lessons across learning environments within the school. We provide a narrative account of our early work in using this theoretical framework to co-plan and enact interdisciplinary mathematics and computer science (CS) tasks with a team of elementary school educators and school district personnel. The unit focuses on the concepts of exponents in mathematics and repeat loops as a control structure in computer science. Using a narrative approach, we describe what occurred during the collaborative planning of lessons and subsequent enactments in two fifth-grade classrooms and one computer lab and provide a practitioner-oriented account of our experience.