While semiconductor spintronics promises lower switching energy and faster speed, a major limitation on its development as a viable technology is the lack of room temperature ferromagnetic semiconductor materials. The material challenge is great, because not only magnetic and electronic doping but also thermally robust coupling between them are required for a room temperature ferromagnetic semiconductor. Here, we report the growth-controlled engineering of magnetic exchange interactions in single crystalline GaCoZnO1-v epitaxial films with high Co concentrations (0.3 ≤ x ≤ 0.45) by controlling oxygen vacancy and carrier density through Ga3+ doping. Strong ferromagnetism, spin-split impurity states, and spin-polarized electrical transport are realized and well controlled at room temperature by tailoring the s,p-d exchange coupling. This room temperature ferromagnetic semiconductor, which offers the ability to individually control carrier density and magnetic doping, will lay a solid foundation for the development of practical spintronic devices operating at room temperature.