A Burstein-Moss shift has been observed in highly transparent conducting zinc oxide films prepared by ion-beam-assisted reactive deposition. The optical gaps ranged from 3.27 to 4.1 eV increase with an increase in film conductivities and carrier concentrations. Annealing over 773 K reduces conductivities by several orders of magnitude and subsequently narrows the optical gaps from 3.41 to 3.24 eV. When the films are irradiated with a UV light, they exhibit some photoresponse. The observed UV photoresponse can be interpreted using oxygen photodesorption and chemisorption at the surface.