Ga-substituted magnetic garnet films are laser annealed with annealing times of several milliseconds by scanning a cw argon laser beam across the film. Locally the bubble collapse field and the saturation magnetization increase, and the domain width decreases permanently unless conventional furnace annealing is used to restore the material to its initial state. We attribute the observed effects to a crystallographic site redistribution of the Ga and the Fe atoms in annealed regions which support mobile bubbles. The site distribution is changed from a state quenched in from the growth temperature to a higher-temperature state representative of the laser-annealing treatment. The effect does not involve melting.