  We present the results of CO(1-0) emission mapping with the IRAM
interferometer, at \sim 1 arcsec, resolution, of the z=0.223 ultra-luminous
starburst IRAS 11582+3020. This galaxy was selected from an IRAM-30m survey of
30 galaxies at moderate redshift (z \sim 0.2-0.6) to explore galaxy evolution
and in particular the star formation efficiency, in the redshift range filling
the gap between local and very high-z objects. The CO emission is kinematically
resolved, and about 50% of the total emission found in the 27 arcsec (97 kpc)
single dish beam is not recovered by the interferometer. This indicates that
some extended emission may be present on large scales (typically 7-15 arcsec).
The FIR-to-CO luminosity ratio follows the trend between local and high-z
ultra-luminous starbursts.
