This was a qualitative study of the influence of Research Experiences for STEM Educators and Teachers (RESET) on a teachers' classroom practices and identities. RESET is a year-long professional development and research experience for teachers supported through the Army Educational Outreach Program (AEOP). This research study inductively analyzed 88 surveys, 15 interviews, and 36 participant journals from middle and high school STEM teachers in the United States who participated in the RESET program to identify the components of pedagogy, community of practice, unit plan development, research experience, and exposure to STEM scientists and researchers that may have influenced a change in classroom practice or identity. Teachers reported their practice was considerably influenced (41%) or somewhat influenced (41%) by participation in the RESET program. This influence decreased over time and increased with the number of times the teacher participated in the program. The laboratory research component was the most influential in changing teachers' classroom practices. In decreasing order, the other influential components were STEM unit plan development (78% of teachers implemented the lesson they developed), pedagogy, community of practice, and STEM career exposure. Looking at the data over time, the farther away teachers got from their time in the RESET program, the less it influenced their classroom practice. The more times teachers participated in the program, the more likely they reported their teaching practice had been considerably changed. Participation in the program did not change a teacher's identity into a researcher. However, it gave the teachers more confidence in the classroom and in interactions with their peers. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]