  Rich galaxy clusters are powerful probes of both cosmological and galaxy
evolution parameters. The CNOC cluster survey was primarily designed to
distinguish between Omega=1 and Omega~0.2 cosmologies. Projected foreground and
background galaxies provide a field sample of comparable size. The results
strongly support a low-density universe. The luminous cluster galaxies are
about 10-30% fainter, depending on color, than the comparable field galaxies,
but otherwise they show a slow and nearly parallel evolution. On the average,
there is no excess star formation when galaxies fall into clusters. These data
provide the basis for a simple Lambda measurement using the survey's clusters
and the field data. The errors in Omega_M, Lambda, sigma_8 and galaxy evolution
parameters could be reduced to a few percent with a sample of a few hundred
clusters spread over the 0<z<1 range.
