  We examine the red fraction of central and satellite galaxies in the large
zCOSMOS group catalog out to z ~ 0.8 correcting for both the incompleteness in
stellar mass and for the less than perfect purities of the central and
satellite samples. We show that, at all masses and at all redshifts, the
fraction of satellite galaxies that have been quenched, i.e., are red, is
systematically higher than that of centrals, as seen locally in the Sloan
Digital Sky Survey (SDSS). The satellite quenching efficiency, which is the
probability that a satellite is quenched because it is a satellite rather than
a central, is, as locally, independent of stellar mass. Furthermore, the
average value is about 0.5, which is also very similar to that seen in the
SDSS. We also construct the mass functions of blue and red centrals and
satellites and show that these broadly follow the predictions of the Peng et
al. analysis of the SDSS groups. Together, these results indicate that the
effect of the group environment in quenching satellite galaxies was very
similar when the universe was about a half its present age, as it is today.
