The MiniBooNE Collaboration reports initial results from a search for ν̅ μ→ν̅ e oscillations. A signal-blind analysis was performed using a data sample corresponding to 3.39×1020 protons on target. The data are consistent with background prediction across the full range of neutrino energy reconstructed assuming quasielastic scattering, 200<EνQE<3000  MeV: 144 electronlike events have been observed in this energy range, compared to an expectation of 139.2±17.6 events. No significant excess of events has been observed, both at low energy, 200–475 MeV, and at high energy, 475–1250 MeV. The data are inconclusive with respect to antineutrino oscillations suggested by data from the Liquid Scintillator Neutrino Detector at Los Alamos National Laboratory.