Fe films have been prepared in ultrahigh vacuum by epitaxial growth on MgO(001) substrates. Spin-resolved inverse photoemission measurements indicate that nonannealed overlayers display lower spectroscopic quality than the corresponding bulk system. Low energy electron diffraction and x-ray photoemission reveal that annealing promotes oxygen surface segregation giving rise to a c(2 x 2) reconstruction even in several hundred Angstrom thick films. It is found that high-quality Fe(001) single crystal films with clean and well ordered surfaces can be obtained after high temperature annealing (similar to 600 degrees C) of relatively thick films (>1000 Angstrom).