  To test whether clusters have rising mass to light ratios at large radii and
to estimate the amplitude of the density fluctuation spectrum on the scale of
10\hmpc\ the Canadian Network for Observational Cosmology (CNOC) cluster
collaboration is obtaining Multi-Object Spectrograph velocities and two colour
photometry for a sample of $\simeq$1000 cluster galaxies and $\simeq$2000 field
galaxies in a 5\hmpc\ neighborhood of high X-ray luminosity clusters at
$z\simeq 0.3$. X-ray selection of the cluster sample picks out objects on the
basis of the depth of their potential well depth, and is insensitive to both
projection effects and galaxy biases. The galaxy dataset, with selection
controlled using automated photometry, automated mask design, spectral
selection modeling, and accurate velocities, will be the best available at any
redshift for our tests. Measuring mass-to-light ratios (M/L) at large radii
requires a statistical removal of field galaxies projected into the redshift
space of the cluster. This can be done relatively accurately for moderate
redshift clusters, using the large number of foreground and background
galaxies. The CNOC sample also provides a sensitive test of the density
fluctuation spectrum on cluster scales. The 30 or so redshifts available in
each of three clusters gives an average velocity dispersion of about 1000 \kms
which indicates that the $\sigma_8$ normalization parameter is in the range of
$0.6\lta \sigma_8\lta 0.9$.
