Tungsten−aluminum oxide granular films with metal volume fraction, x, varying from 0.9 to 0.15 were prepared by an rf sputtering technique in which the entire compositional range was simultaneously deposited. At the metal−rich end the tungsten particles are mainly in the normal bcc form (α−W). As x decreases, the amount of tungsten in the β phase (A−15 structure) increases. At x∠0.3 the tungsten is all β−W. In the as−prepared films the particle size, as determined by x−ray line broadening, varies from ∠65 Å to ∠25 Å as x varies from 0.9 to 0.15. Annealing the films results in particle growth and an increase in the amount of α phase. The β phase persists in these granular films to much higher temperatures than reported elsewhere. It is proposed that the metastable β−W phase is stabilized by the very small crystallite size.