MINOS is a long baseline neutrino oscillation experiment. A manmade beam of predominantly muon neutrinos is detected both 1 km and 735 km from the production point by two functionally identical detectors. A comparison of the energy spectra measured by the two detectors shows the energy-dependent disappearance of muon neutrinos characteristic of oscillations and allows a measurement of the parameters governing the oscillations. This thesis presents work leading to measurements of disappearance in the 6% ∇_μ background in that beam. A calibration is developed to correct for time-dependent changes in the responses of both detectors, reducing the corresponding uncertainty on hadronic energy measurements from 1.8% to 0.4% in the near detector and from 0.8% to 0.4% in the far detector. A method of selecting charged current ∇_μ events is developed, with purities (efficiencies) of 96.5% (74.4%) at the near detector, and 98.8% (70.9%) at the far detector in the region below 10~GeV reconstructed neutrino energy. A method of using the measured near detector neutrino energy spectrum to predict that expected at the far detector is discussed, and developed for use in the ∇_μ analysis. Sources of systematic uncertainty contributing to the oscillation measurements are discussed. In the far detector, 32 ∇_μ events are observed below a reconstructed energy of 30 GeV, compared to an expectation of 47.8 for Δm̄²_atm = Δm²_atm, sin²(2‾θ₂₃) = sin²(2θ₂₃). This deficit, in such a low statistics sample, makes the result difficult to interpret in the context of an oscillation parameter measurement. Possible sources for the discrepancy are discussed, concluding that considerably more data are required for a definitive solution. Running MINOS with a dedicated ∇_μ beam would be the ideal continuation of this work.

MINOS (Main Injector Neutrino Oscillation Search) experiment has been designed to search for a change in the avor composition of a beam of muon neutrinos as they travel between the Near Detector at Fermi National Accelerator Laboratory and the Far Detector in the Soudan mine in Minnesota, 735 km from the target. The MINOS oscillation analysis is mainly performed with the charged current (CC) events and sensitive to constrain high-delta m2 values. However, the quasi-elastic (QEL) charged current interaction is dominant in the energy region important to access low-delta m2 values. For further improvement, the QEL oscillation analysis is performed in this dissertation. A data sample based on a total of 2.50 x 1020 POT is used for this analysis. In summary, 55 QEL-like events are observed at the Far detector while 87.06 +/- 13.17 (syst:) events are expected with null oscillation hypothesis. These data are consistent with vm disappearance via oscillation with delta m2 = 2.10 +/- 0.37 (stat:) +/- 0.24 (syst:) eV2 and the maximal mixing angle.