Long term thermal stability is a prerequisite for bubble film materials. Some results of an investigation of the isothermal annealing behavior of amorphous Gd‐Co‐Mo thin films, in the temperature range 150°‐350°C, are being reported. All functional magnetic properties were retained by these films even after annealing at 350°C. The room temperature magnetization and the stripe collapse field decreased upon annealing and then stabilized, the magnitude of the decrement depending on the annealing temperature. The activation energy associated with the annealing process is about 0.4 eV. The results are interpreted in terms of corresponding changes in the compensation temperature, and they indicate that stabilization of the magnetic properties prior to bubble device fabrication may be a desirable process step.