Ni-based catalysts generated by in situ reduction of MNiOx (M: La, Sr and Ce) were investigated in the methane Oxy-CO2 reforming reaction. The precursors and catalysts were characterized by X-ray diffraction, Thermoprogrammed Reduction and Oxidation - TPR/TPO, Superficial Thermoprogrammed Reaction - TPSR, High-Resolution transmission electron microscopy and Raman spectroscopy. The addition of strontium gave rise to a less active catalyst, due to the formation of SrCO3, whose presence blocks the reactants access to the nickel active sites. It was found that the replacement of lanthanum with cerium led to an increase in the overall activity of the catalysts, favoring the breakdown of the C-H bond, and suggesting a mechanism of coke oxidation by the lattice oxygen.