Science, Technology, Engineering, and Mathematics (STEM) education has become increasingly important in the US due to its influence on the nation's educational needs, the creation of a skilled labor force, and opportunities for more tech-savvy workers. However, the evaluation approaches and methodologies used in STEM education programs have come under examination in recent times, with questions being raised in the evaluation literature. Evaluation practitioners in STEM education come from diverse backgrounds, hold different worldviews, and subscribe to a growing list of evaluation approaches. These practitioners value quantitative, qualitative, or mixed methods in evaluation objectives, questions posed, study design, implementation, report writing, and dissemination. This dissertation is sequential qualitative research that examined the Discourse of STEM education evaluation from a practitioner's perspective. It focused on the dominant evaluation approaches and methodologies while reviewing AEA STEM TIG abstracts and conducting individual interviews with STEM education evaluators. The research revealed the varied landscape of evaluation approaches stemming from differing values, training, and interests of evaluators. The study also illuminated the philosophical underpinnings of method choices that shape evaluation methodologies. Several findings emerged from this research. These include STEM education evaluators' discussion on lessons learned, challenges, and impact on STEM education evaluation practice. Furthermore, collaborative evaluation approaches were frequently used to understand the complexity of STEM education programs, and mixed methodologies were used to strengthen studies by incorporating both qualitative and quantitative approaches. STEM education evaluators from academic, private, and public sectors discussed program planning, implementation, and professional development for educators, as well as the use of technology in practice. Differences emerged, with academic evaluators focusing on cultural context, undergraduate research mentorship, and evaluation instruments, private evaluators emphasizing fidelity of implementation, data collection, and collective impact measurements, and public evaluators caring about program culture, career plans, work-life balance, and workforce trajectories. STEM education evaluators emphasized the importance of equity in broadening participation, spoke positively about professional development and community organizing, noted the evolution of accountability through leadership, social justice, and self-socialization, recognized the significant influence of new technology on data utilization in evaluation, and discussed new approaches and methodologies to advance STEM education evaluation. The STEM evaluation literature identifies various evaluation approaches that resonate with STEM education evaluators. Evaluators in the STEM fields are mostly interested in Client-Centered/Responsive and Utilization-Focused Evaluation Approaches. Academic and private sector evaluators share common ground in Collaborative/Partnership Approaches, Culturally Responsive Evaluation, Outcome/Value-Added Assessment, and Decision/Accountability. In addition, evaluators in the STEM fields justify their evaluation methodologies with data collection devices, status, and surveys. In conclusion, STEM education evaluation approaches are constantly evolving and influenced by various contexts. Evaluators from different sectors have different viewpoints on the current and future direction of the field. However, STEM education evaluators emphasize the importance of equity in broadening participation, professional development, community organizing, and the use of technology in practice. Further exploration of the Discourse around STEM education evaluation methodologies is needed to clarify the philosophical assumptions underlying evaluation methods. [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/en-US/products/dissertations/individuals.shtml.]