The effect of materials processing on structural and low-frequency dielectric properties of SrTiO3 (ST) ceramics doped with MgO is studied in this work. Samples prepared with agate milling media show negligible solubility of MgO in ST. Instead, MgO was present in a SiO2 rich phase at the grain boundaries. For some compositions containing this phase, a dielectric permittivity peak was present at low temperatures associated with an extra Raman vibrational mode. In contrast, samples prepared with teflon pots and ZrO2 media exhibit a higher solid solubility limit of Mg in ST, absence of second phase at the grain boundaries and no dielectric anomaly at low temperatures for the same batched compositions.