  We present high signal-to-noise optical spectra for 67 low-redshift (0.1 < z
< 0.4) galaxies that lie within close projected distances (5 kpc < rho < 150
kpc) of 38 background UV-bright QSOs. The Keck LRIS and Magellan MagE data
presented here are part of a survey that aims to construct a statistically
sampled map of the physical state and metallicity of gaseous galaxy halos using
the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST). We
provide a detailed description of the optical data reduction and subsequent
spectral analysis that allow us to derive the physical properties of this
uniquely data-rich sample of galaxies. The galaxy sample is divided into 38
pre-selected L ~ L*, z ~ 0.2 "target" galaxies and 29 "bonus" galaxies that lie
in close proximity to the QSO sightlines. We report galaxy spectroscopic
redshifts accurate to +/- 30 km s-1, impact parameters, rest-frame colors,
stellar masses, total star formation rates, and gas-phase interstellar medium
oxygen abundances. When we compare the distribution of these galaxy
characteristics to those of the general low-redshift population, we find good
agreement. The L ~ L* galaxies in this sample span a diverse range of color
(1.0 < u-r < 3.0), stellar mass (10^9.5 < M/M_sun < 10^11.5), and SFRs (0.01 -
20 M_sun yr-1). These optical data, along with the COS UV spectroscopy,
comprise the backbone of our efforts to understand how halo gas properties may
correlate with their host galaxy properties, and ultimately to uncover the
processes that drive gas outflow and/or are influenced by gas inflow.
