Context : Oxygen is the third most common element in the Universe .
The measurement of oxygen lines in metal-poor unevolved stars , in particular near-UV OH lines , can provide invaluable information about the properties of the Early Galaxy .

Aims : Near-UV OH lines constitute an important tool to derive oxygen abundances in metal-poor dwarf stars .
Therefore , it is important to correctly model the line formation of OH lines , especially in metal-poor stars , where 3D hydrodynamical models commonly predict cooler temperatures than plane-parallel hydrostatic models in the upper photosphere .

Methods : We have made use of a grid of 52 3D hydrodynamical model atmospheres for dwarf stars computed with the code \mathrm { CO } ^ { 5 } \mathrm { BOLD } , extracted from the more extended CIFIST grid .
The 52 models cover the effective temperature range 5000–6500 K , the surface gravity range 3.5–4.5 and the metallicity range -3 < [ { Fe } / { H } ] < 0 .

Results : We determine 3D-LTE abundance corrections in all 52 3D models for several OH lines and Fe i lines of different excitation potentials .
These 3D-LTE corrections are generally negative and reach values of roughly -1 dex ( for the OH 3167 with excitation potential of approximately 1 eV ) for the higher temperatures and surface gravities .

Conclusions : We apply these 3D-LTE corrections to the individual O abundances derived from OH lines of a sample the metal-poor dwarf stars reported in Israelian et al .
( 1998 , 2001 ) and Boesgaard et al .
( 1999 ) by interpolating the stellar parameters of the dwarfs in the grid of 3D-LTE corrections .
The new 3D-LTE [ O/Fe ] ratio still keeps a similar trend as the 1D-LTE , i.e , increasing towards lower [ Fe/H ] values .
We applied 1D-NLTE corrections to 3D Fe i abundances and still see an increasing [ O/Fe ] ratio towards lower metallicites .
However , the Galactic [ O/Fe ] ratio must be revisited once 3D-NLTE corrections become available for OH and Fe lines for a grid of 3D hydrodynamical model atmospheres .