Despite being identified as an essential scientific practice, argumentation is rarely integrated into instruction. This could be influenced by teachers' pedagogical design capacity (PDC), which considers teaching as a design activity influenced by both instructional resources (such as tools and professional development (PD)) and teacher resources (such as beliefs and pedagogical content knowledge (PCK)). In this study, we investigated how the development of five upper elementary and middle school teachers' beliefs and PCK impacted their design and integration of argumentation within their instruction. Data sources included pre- and postsurveys, videotaped lessons, and interviews. Our analyses resulted in two groups of teachers. While several teachers "offloaded" some of their lesson design by using PD resources, others adapted the PD resources and renamed an aspect of their current instruction as argumentation. Moreover, the teachers who "offloaded" some of their lesson design exhibited argumentation within their instruction and greater change in their beliefs or PCK for argumentation. This suggests the importance of future teacher education experiences supporting teachers' PDC by providing multiple opportunities to offload, try out, and reflect on instruction. Future research should explore whether teachers understanding of the PDC framework supports their understanding of argumentation.