A light-scattering photometer with optical microscope for in situ morphological studies of extruded polymer blends is described. The optics for light scattering and microscopy can be switched back and forth via simple translation of a rail-mounted optical platform without realignment, allowing efficient measurements in both real and reciprocal space during polymer processing. Blends of polystyrene and polyethylene are used to demonstrate the performance and versatility of the instrument.