  We have performed a detailed oxygen abundance analysis of 23 metal-poor
(-3.0<[Fe/H]<-0.3) unevolved halo stars and one giant through the OH bands in
the near UV, using high-resolution echelle spectra. Oxygen is found to be
overabundant with respect to iron in these stars, with the [O/Fe] ratio
increasing from 0.6 to 1 between [Fe/H]=-1.5 and -3.0. The behavior of the
oxygen overabundance with respect to [Fe/H] is similar to that seen in previous
works based on OI IR triplet data (Abia and Rebolo 1989; Tomkin et al. 1992;
Cavallo, Pilachowski, and Rebolo 1997). Contrary to the previously accepted
picture, our oxygen abundances, derived from low-excitation OH lines, agree
well with those derived from high-excitation lines of the triplet. For nine
stars in common with Tomkin et al. we obtain a mean difference of 0.00+/-0.11
dex with respect to the abundances determined from the triplet using the same
stellar parameters and model photospheres. For four stars in our sample we have
found measurements of the [OI] 6300 A line in the literature, from which we
derive oxygen abundances consistent (average difference 0.09 dex) with those
based on OH lines, showing that the long standing controversy between oxygen
abundances from forbidden and permitted lines in metal-poor unevolved stars can
be resolved. Our new oxygen abundances show a smooth extension of the
Edvardsson et al.'s (1993) [O/Fe] versus metallicity curve to much lower
abundances, with a slope -0.31+/- 0.11 (taking into account the error bars in
both oxygen abundances and metallicities) in the range -3<[Fe/H]<-1.
