MZR of zCOSMOS ELOX 0.5 <z< 0.75 galaxies (red circles) and galaxies with O/H measurements based on additional ISAAC spectroscopy (green filled circles), compared to the local MZR of Tremonti et al. (2004) and the MZR at 0.75 <z< 0.82 found by Zahid et al. (2011) using the DEEP2 sample. The individual DEEP2 data are shown as cyan symbols, while the mean DEEP2 MZR from Eq. (8) in Zahid et al. (2011), converted to the KD02 calibration, is shown as a blue line. The mean O/H values of zCOSMOS galaxies in three mass bins are shown as large magenta filled circles. While both zCOSMOS and DEEP2 galaxies at z ~ 0.5−0.8 have similar (slightly lower) metallicities at the higher masses compared to z ~ 0, a population of galaxies with metallicities lower by a factor 2−3 than SDSS exists at the lowest masses probed by zCOSMOS and DEEP2.