  We revisit the Galactic chemical evolution of oxygen, addressing the
systematic errors inherent in classical determinations of the oxygen abundance
that arise from the use of one dimensional hydrostatic (1D) model atmospheres
and from the assumption of local thermodynamic equilibrium (LTE). We perform
detailed 3D non-LTE radiative transfer calculations for atomic oxygen lines
across a grid of 3D hydrodynamic stag- ger model atmospheres for dwarfs and
subgiants. We apply our grid of predicted line strengths of the [OI] 630 nm and
OI 777 nm lines using accurate stellar parameters from the literature. We infer
a steep decay in [O/Fe] for [Fe/H] $\gtrsim$ -1.0, a plateau [O/Fe] $\approx$
0.5 down to [Fe/H] $\approx$ -2.5 and an increasing trend for [Fe/H] $\lesssim$
-2.5. Our 3D non-LTE calculations yield overall concordant results from the two
oxygen abundance diagnostics.
