In this paper, we study the use of spectral information in measuring neutrino oscillation parameters in a superbeam. Low-energy neutrino interactions are dominated by quasi-elastic charged-current interactions, where the final state is solely composed of a lepton and a proton. In water Cerenkov detectors the proton is below detection threshold and the only visible particle is the lepton. Using knowledge of the beam direction it is possible to reconstruct the neutrino energy from lepton information alone, but this reconstruction is heavily affected by nuclear physics effects and detector resolution. We show that it is possible to unfold such effects using a Monte Carlo reweighting technique, and present details of the method and improvements on examples of fits to oscillation parameters.