This study investigated the relationship between prospective secondary mathematics teachers' perspectives and their mathematical knowledge for teaching in action. Data from two prospective teachers' practice-teachings, one in geometry and one in algebra, their lesson plans and self-reflections were analyzed with Teacher Perspectives and Knowledge Quartet frameworks. Results showed that prospective teachers who thought of mathematics and mathematics learning as dependent on the knower, corresponding with a progressive incorporation perspective, had demonstrated all the codes in Knowledge Quartet Framework. These results suggest that, once prospective teachers are given opportunities to develop a progressive incorporation perspective on mathematics, mathematics learning, and mathematics teaching during methods and practice teaching courses, this might contribute to the developments in their mathematical knowledge for teaching in action, independent of the particular concept they teach. Suggestions for developing a progressive incorporation perspective during methods and practice teaching courses are given.