The electroabsorption spectra within the range of nickel donor excitons in the semiconductors ZnSe:Ni and ZnO:Ni are presented. The defect vibrations in a crystal of ZnSe:Ni induced by Ni impurity ions having a charge state of + 1 with respect to the lattice are described. The calculations have been carried out in the framework of a recursive scheme in a shell model. Model calculations have enabled an interpretation of the vibronic structure in the electroabsorption spectra of Ni donor excitons in crystals of ZnSe:Ni and ZnO:Ni. The most intense vibrational replicas of the Ni donor exciton zero-phonon line appears to have a combination character ωII + nωI.