A microscopy probe designed for use in high field magnets is presented. It was developed to observe and continuously measure the position and shape of a magnetically driven grain boundary in a magnetically anisotropic material. The approach utilizes the anisotropy of reflectivity of visible light for orientation contrast to determine the boundary location. The major components of the system are the polarizing microscope with video camera and the sample chamber with a resistive heater for annealing at elevated temperatures up to 500 degrees C in an inert gas atmosphere. The results of test measurements are presented.