Reform efforts in K-12 science education have been gaining pace ever since the introduction of the "Next Generation Science Standards" (NGSS). The new vision calls for reconsidering teacher preparation programs to prepare future teachers who are confident and competent in delivering NGSS-based instruction. This study investigated the development of 27 preservice secondary science and mathematics teachers' (PSTs') knowledge and skills as they understand, interpret, and implement the NGSS, particularly science and engineering practices (SEPs), within the context of microteaching during a STEM methods course. Primary data sources include 12 videos of 40-min-long microteaching lessons, self-reflections, semi-structured and focus-group interviews, and artifacts such as student-designed science lesson plans. This qualitative study utilizes deductive-inductive and thematic analysis approaches to analyze PSTs microteaching videos to understand how various SEPs were enacted and integrated within the science lessons. While the average duration of the occurrence of each SEP varied, SEP 1 (Asking questions) showed the least occurrence compared to other SEPs across lessons. Most PSTs reported a better understanding of the NGSS framework at the end of the semester and found it a useful tool for planning a science lesson. Implications for preservice secondary STEM teacher education programs are discussed.