We have investigated cross sections for the excitation of the 2p33s 5So, 3So, 2p33p 5P, 3P, 2p33d 3Do, 2p33s' 3Do, 2p33s'' 3Po and 2s2p5 3Po states by electron impact using a modified R-matrix method based on the B-spline representation of the scattering orbitals in the energy region from threshold to 100 eV. The 26 spectroscopic bound and autoionizing states of atomic oxygen have been included in the close-coupling expansion. We have also carried out calculations in 8 and 16 state close-coupling approximations and in the Born approximation. We have obtained an accurate representation of the target wavefunctions on the basis of non-orthogonal orbitals, and we compare the present results with other calculations and experiments. Significant discrepancies in the shape and magnitude of cross sections for some of the transitions are noted.