Penning ionization of CH3OH, (CH3)(2)O, and (CH3CH2)(2)O upon collision with He*(2(3)S) metastable atoms was studied by collision-energy-resolved Penning ionization electron spectroscopy. Collision energy dependence of the partial ionization cross sections indicates that the interaction potentials are strongly anisotropic between He-*(2(3)S) and the molecules investigated. In the studied energy range, the interaction potential was found to be repulsive around the methyl End the ethyl group and attractive around the oxygen atom. The ionization band for the pi orbitals delocalized widely in the direction perpendicular to the C-O-H or C-O-C plane of CH3OH, (CH3)(2)O, and (CH3CH2)(2)O seems to be very enhanced in the Penning ionization electron spectra.