COVID-19 has presented new challenges for all teachers, especially teachers of students with special needs. Students have struggled with online learning environments with limited opportunities for social interaction and resources for these disruptive times. The study examined the effect of a professional development (PD) intervention, guided by the inquiry-based learning framework (IBL) to prepare special education teachers to engage students with disabilities for online teaching. This PD intervention used assistive technology (AT) as a catalyst for helping teachers to develop competencies in designing inquiry-based learning experience for online teaching. The research study utilized the sequential mixed methods approach to collect both quantitative and qualitative data. Findings showed that the structure and content of PD supported development of special education teachers' competency in designing AT-infused inquiry-based experience for students with disabilities. The study also indicated that development of AT competency was a non-linear process that was moderated by various contextual and personal factors.