This qualitative case study explains how teachers with high or low self-efficacy adapted to changing teaching demands for online learning during the COVID-19 pandemic. The study considers how teachers adapted to online learning during the COVID-19 school closings using Bandura's (1971) SET as a theoretical framework. The findings suggest that a person can exhibit one, two, three, or all four self-efficacy tenets on any one day. The four tenets of self-efficacy are enactive mastery experiences, vicarious experiences, verbal persuasion, and physiological arousal and affective states. The results also imply that there were similarities and differences in the transitions and adaptations to asynchronous online instruction that teachers with high and low self-efficacy made to meet student learning needs during the pandemic. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]