Deep optical imaging in the B and R band of about 50 luminous radio galaxies and radio QSOs in the redshift range 0.1-0.5 is reported. More than 80 percent of each type of object are optically interacting; about 60 percent are irregular in some way, and about 30 percent have tidal tails. Separations range from a few kpc to tens of kpc. About 30 percent of the objects have elliptical galaxy characteristics and none has spiral. The mean optical absolute magnitude of radio galaxies is fainter by 1 mag than the host galaxies of QSOs, and the distributions differ significantly. Radio galaxies are redder and larger and have smaller luminosity scale lengths than QSO hosts. Thus, they are a different sample of objects. In all objects, however, galaxy size is greatest at M(R) of about -22, and at the lower redshifts. 30 references.