Pre- and in-service teachers' professional development is critical in the lifelong learning era. This case study explores 27 pre- and in-service teachers' reasons for selecting a MOOC, their learning experiences, and their perceptions of the value for their professional development. Data sources in this study included: 1) MOOC reviews written and submitted by the participants 2) extended versions of MOOC reviews into research papers, 3) descriptions of MOOCs taken by the participants. Findings of this study indicated that MOOCs served as tremendous resources for multiple learning purposes, evidenced by the voices of these 27 participants. In addition, the multiple pedagogical approaches found in the MOOCs offered great experiential learning spaces for these K-12 pre- and in-service teachers who drew instructional lessons to apply to their current and future professional endeavors.