We examine the evolution of the galaxy luminosity function (LF) using a sample of over 2000 galaxies, with 0.12< z< 0.55 and 17.0< R < 21.5, drawn from the Canadian Network for Observational Cosmology Field Galaxy Redshift Survey (CNOC2), at present the largest such sample at intermediate redshifts. We use UBVR I photometry and the spectral energy distributions (SEDs) of Coleman, Wu, and Weedman to classify our galaxies into early, intermediate, and late types, for which we compute LFs in the rest-frame B, R , and U bandpasses. In particular, we adopt a convenient parameterization of LF evolution including luminosity and number density evolution and take care to quantify correlations among our LF evolution parameters. We also carefully measure and account for sample selection effects as functions of galaxy magnitude and color.