The IceCube Neutrino Observatory at the South Pole is a Cherenkov-based detector inside antarctic ice with a volume of about 1 cubic kilometer. IceCube consists of 5160 Digital Optical Modules (DOMs) attached like beads on 86 vertical strings, instrumenting depths from 1450 - 2450 m below the surface of the glacier. The bottom central region of IceCube has densely spaced DOMs and is known as DeepCore, which is capable of detecting atmospheric neutrinos at GeV energies. Atmospheric neutrinos can be used to study neutrino oscillations over wide ranges of energies and baselines. We present a measurement of the oscillation parameters $\Delta m^2_{32}$ and $\theta_{23}$ using the disappearance of atmospheric muon neutrinos with a new data sample from IceCube DeepCore. This sample consists of improved data calibration, detector simulation, and data processing, as well as a more sophisticated treatment of systematics. These results are of comparative precision to measurements from long-baseline neutrino oscillation experiments.