  We study the cross-correlation between 716 MgII quasar absorption systems and
about 100,000 Luminous Red Galaxies (LRGs) selected from the Sloan Digital Sky
Survey Data Release 3 in the redshift range 0.4<z<0.8. The MgII systems were
selected to have 2796 & 2803 rest-frame equivalent widths greater than 1.0 \AA
and identifications confirmed by the FeII 2600 or MgI 2852 lines. Over
co-moving scales 0.2--13/h Mpc, the MgII--LRG cross-correlation has an
amplitude 0.69+/-0.09 times that of the LRG--LRG auto-correlation. Since LRGs
have halo-masses of 10^{13} \msun, this strong cross-correlation implies that
the absorber host-galaxies have halo-masses 1--2 times 10^{12} \msun.
