Composite materials are provided which include a glass-ceramic matrix composition that is lightly crystallized, a fiber reinforcement within the glass-ceramic matrix composition which remains stable at temperatures greater than 1400° C., and an interphase coating formed on the fiber reinforcement. A method of making a composite material is also provided, which includes applying heat and pressure to a shape including fiber reinforcements and glass particles. The heat and pressure lightly crystallize a matrix material formed by the heat and pressure on the glass particles, forming a thermally stable composite material.