In the present article we show that, although the reflux method is not common for the synthesis of multicomponent MoVTeNbO catalysts, an optimized reflux synthesis of metallic precursors leads to efficient materials for the oxidative dehydrogenation of ethane and the selective oxidation of propane into acrylic acid, with the results at the same level as those of the best catalysts reported in the literature to date. It has been demonstrated that the reflux temperature is of paramount importance to achieve active and selective catalysts. Thus, the incorporation of vanadium and niobium to a polyoxometalate in the catalyst precursors is favored by refluxing at 110 °C, promoting the formation of the desired orthorhombic M1 phase. Additionally, the incorporation in the synthesis gel of cations such as ammonium or methylammonium provokes a further improvement of the catalytic performance whenever the activation procedure is carefully controlled.