We present low temperature cathodoluminescence (CL) studies of relaxed Ge x Si 1− x , selectively grown on a patterned Si (111) substrate by liquid phase epitaxy, using heteroepitaxial lateral overgrowth. In the spectrally resolved CL of the resulting GeSi crystals, we observe an emission peak attributed to the recombination of free excitons (FEs). We further observe a peak of lower intensity at a lower energy position, caused by the unresolved phonon replicas of the FE peak. At an even lower energy position, we observe a comparatively broad luminescence band, attributed to CL from dislocations. Monochromatic images using the FE emission, or its phonon replica, reveal three types of contrast variations. On a 5 μm scale we observe dark line defects in the GeSi crystals, which we attribute to dislocations. In the lateral position of the seeding windows for the epitaxy, the GeSi crystals exhibit a dark, 20 μm wide band. On a 20 to 50 μm scale we observe small fluctuations in the Ge x Si 1− x composition, which manifests itself as local intensity variations with detection wavelength.