Magnesium-lanthanum-mixed oxide catalysts with different Mg/La ratios are prepared by coprecipitation at a constant pH method. The prepared catalysts were characterized by various techniques, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of CO2 (CO2-TPD), and Brunauer-Emmett-Teller (BET) surface area. These catalysts are evaluated for transesterification of both edible and nonedible oils to their corresponding fatty acid methyl esters. The catalyst with a Mg/La weight ratio of 3:1 is showing optimum performance toward transesterification of oils, and it exhibited excellent activity even at room temperature. The disclosed catalyst is also tolerable for the transesterification of oils containing both water and free fatty acids. The catalyst can be easily recovered and reused with consistent activity. The exceptional activity of the Mg/La (3: 1) catalyst during transesterification is endorsed because of the presence of the highest number of strong basic sites as evidenced by CO2-TPD compared to other Mg/La analogues. The higher basic strength of Mg/La (3: 1) is also evidenced by XPS measurements, because the catalyst showed a negative shift in O1s binding energy, which indicates the presence of strong basic sites.