The integration of 21st-century skills into education systems has significantly increased the importance of STEM education. In this context, the STEM SOS model emerges as an innovative instructional approach that combines project-based learning (PBL) with inquiry-based learning, promoting interdisciplinary and student-centered learning. This chapter provides a detailed overview of the theoretical foundations of the STEM SOS model, the structured project levels (Level I, II, and III), and its impact on student learning processes. It highlights how the model supports students in gaining critical competencies such as scientific inquiry, problem-solving, collaboration, creative thinking, and communication. Furthermore, the chapter discusses the model’s positive impact on female students and minority groups, emphasizing its potential to increase interest and career orientation in STEM fields. Through engagement with real-world problems, students are encouraged to develop interdisciplinary products and achieve meaningful learning with technology integration. The model aims to equip learners with essential 21st-century workforce skills. Projects conducted under teacher guidance foster students’ responsibility and active participation in their learning process. With its flexible and inclusive structure, the STEM SOS model presents an effective and applicable framework for STEM education practices in Turkey and beyond.