The increasing interest in early and elementary STEM education comes with a need to increase training and support for teachers of children in the early grades. Early and elementary pre-service teacher preparation in science, math, and integrated STEM can play a critical role in enhancing teachers’ self-efficacy and pedagogical content knowledge in these areas. However, few quantitative research studies have been published on this topic, especially involving early childhood and elementary programs. Because few STEM courses are typically offered in these programs, we need courses and experiences that can be transformational. This study evaluates the short- and long-term impacts on pre-service teachers who participated in our STEM Collaboration approach (n=164), which was created to meet this goal through an innovative early childhood and elementary collaboration. Analyses of mixed methods data collected from surveys, tests, open-ended feedback, and a focus group revealed immediate, long-term, and positive impacts on science, math, and integrated STEM self-efficacy and pedagogical content knowledge. Participation in STEM education experiences in pre-service programs that include innovations such as collaboration across colleges and professionalization opportunities made a difference, and one that persisted.