Active learning can have a substantial impact on STEM student learning outcomes. This study used the reasoned action approach to predict the presence of active teaching techniques. Instructor attitudes, perceived social norms, perceived behavioral control and intentions concerning active learning strategies were assessed before and after a teaching workshop, in addition to retrospectively. Behavioral teaching practices were recorded using the Classroom Observation Protocol for Undergraduate STEM (COPUS). Results indicated that instructor attitudes toward and perceived behavioral control over implementing active learning significantly contributed to STEM instructor intentions to use active learning. Further, instructor intentions assessed after the workshop and retrospectively were predictive of instructor behavior. Instructors with high intentions exhibited an increase in 'active' instructor behavior (group work) and a decrease in 'passive' instructor behavior (lecture). These results suggest that whether instructors view active learning as favorable or unfavorable, and whether instructors feel they have control over implementing active learning strategies, is critical to increasing the presence of active teaching intentions and behaviors. Professional development programs wishing to create instructional change should target instructor attitude and control beliefs, as well as discuss normative teaching practices in aim of contributing to instructors' understanding of and future intentions to implement active learning.