  Our research on the age-metallicity and mass-metallicity relations of
galaxies is presented and compared to the most recent investigations in the
field. We have been able to measure oxygen abundances using the direct method
for objects spanning four orders of magnitude in mass, and probing the last 4
Gyr of galaxy evolution. We have found preliminary evidence that the
metallicity evolution is consistent with expectations based on age-metallicity
relations obtained with low resolution stellar spectra of resolved Local Group
galaxies.
