A generalist teacher is one who has been trained and certified to teach multiple core subjects. As the training and certification of generalists can vary greatly between preparation programs, generalists can enter the profession with conflicting beliefs about how a STEM classroom should be structured and facilitated. As few studies focus on perceptions of generalists in STEM, researchers in the current study sought to understand pre-service teachers' perceptions of a STEM clinical experience and determine which factors most affected their perceptions. By determining which factors most affected PSTs' perceptions, researchers hoped to provide suggestions for educator preparation programs so they can better support generalists who end up teaching in STEM classrooms. Researchers interviewed 13 PSTs and 6 in-service teachers and qualitatively analyzed their responses to semi-structured questions. Findings indicated 11 of 13 PSTs devalued the STEM clinical experience, primarily because they were not comfortable with the amount of freedom given to students in the classroom. Two of the 13 PSTs did value the experience, and researchers determined their learner-centered ideologies played a major role. Based on these findings, educator preparation programs can better prepare generalist PSTs for STEM classrooms by: (a) providing more opportunities for generalists to experience authentic STEM classrooms; (b) focusing more on the relationship between ideology and practice; and, (c) creating stronger partnership between preparation programs and K-12 schools.