A new concept is introduced to minimize the oxidation embrittlement problem exhibited by Nicalon fibre-reinforced glass ceramic matrix composites. A small amount of glass is added to the matrix and deforms at temperatures of interest to prevent microcrack formation. The graphitic interphase is thus shielded from an oxidative environment. The composites fabricated with the glass-doped matrices show excellent room- and elevated-temperature strengths and withstand high stresses at elevated temperatures in air for greater than 1 00 h without any deterioration in properties. The modulus of the glass ceramic phase, the stiffness percentage of dopant glass and the process temperature were found to affect composite properties significantly.