Due to the COVID-19 pandemic, school closures were mandated by governments across the globe. This necessitated an abrupt shift to online/distance teaching. Through a mixed-methods study, the authors explored STEM teachers' transition to online teaching and learning in a Canadian context. This subset of the larger study investigated: (1) teachers' views of and attitude toward online teaching; and (2) successes and challenges encountered with online teaching. Data were collected through an online questionnaire administered to 70 Grade 1-12 science/STEM subject teachers in a Canadian province between May and July 2020. Findings are discussed through the lens of self-efficacy theory and the technological pedagogical content knowledge (TPACK) framework. Results indicate that despite few successes, teachers faced a wide array of challenges that negatively affected their attitudes and views toward online teaching, and that the support received did not parallel their expectations. Teachers' experiences, self-efficacy, and technological competency slightly enhanced their views of online teaching but were not sufficient to shift their mindset. Recommendations include effective professional development initiatives and support for teachers to facilitate teachers' transition and enhance their personal views toward online teaching.