Magnesium-based glass matrix composites containing oxide particles were produced by mechanical alloying of Mg₅₅Cu₃₀Y₁₅ elemental powder mixtures with the addition of MgO, CeO₂, Cr₂O₃ or Y₂O₃ oxide particles. The formation of the glassy phase was characterized by X-ray-diffraction and transmission electron microscopy methods and was found to proceed almost unaffected by the presence of the oxides. Differential-scanning-calorimetry-analysis revealed, that the amorphous matrix features a wide supercooled liquid region with an extension of about 40–50 K. Differences in the thermal stability of the composites depending on the oxide addition are discussed. Viscosity measurements proved the existence of a characteristic minimum of viscosity in this temperature range which was used to consolidate the powders into bulk samples by uniaxial hot pressing. The deformation behaviour under compression at room temperature as well as at elevated temperature of 423 K yielded excellent properties compared to conventionally produced magnesium-based alloys.