  Recent accurate abundance analyses of B-type main sequence stars in the solar
vicinity has shown that abundances derived from these stellar objects are more
homogeneous and metal-rich than previously thought. We investigate whether the
inhomogeneity of abundances previously found in B-type stars in the Ori OB1
association is real (hence a signature of enrichment of the newly formed stars
in an induced star formation scenario) or a consequence of intrinsic errors
induced by the use of photometric indices to establish the stellar parameters
prior to the abundance analysis. We obtained a new (improved) spectroscopic
data set comprising 13 B-type stars in the various Ori OB1 associations, and
performed a detailed, self-consistent spectroscopic abundance analysis by means
of the modern stellar atmosphere code FASTWIND. We detect systematic errors in
the stellar parameters determined previously which affect the derived
abundances. Once these errors are accounted for, we find a high degree of
homogeneity in the O and Si abundances for stars in the four Ori OB1 subgroups.
The derived abundances are in very good agreement with recent determinations in
other B-type stars in the solar vicinity. We also compare our results with
those obtained for the Sun during the epoch of the "solar crisis", and the
Orion nebula.
