Orientation dependant behaviour of large grain Ni material is studied in oxidizing atmosphere. Ni/NiO epitaxial relationships are determined using microtexture investigation using GADDS (General Area Detector Diffraction System). The oxide scale texture is determined on each grain of the nickel substrate and it is compared to the data previously determined on a nickel single crystal. Simultaneously, the nickel oxide scale thickness is measured on the same grains using EDX technique. Investigations were performed on two differently orientated grains with a surface of about I mm. In this paper, results concerning the {111} and {511} orientations of nickel grains are described in terms of epitaxial relationships and oxidation rate.