A novel process is introduced for the fabrication of dense, shaped ceramic/metal composites of high ceramic content: the Displacive Compensation of Porosity (DCP) method. In this process, a metallic liquid is allowed to infiltrate and undergo a displacement reaction with a porous oxide preform. Unlike other displacement-reaction-based processes (e.g., the C4, RMP, and AAA processes), a larger volume of oxide is generated than is consumed, so that composites with relatively high ceramic contents can be fabricated. Bar- and disk-shaped MgO/Mg-Al composites were produced by the infiltration and reaction of molten Mg with porous Al2O3 preforms at 1000 °C. By varying the relative density of the preforms (from 53.3 to 71.0% of theoretical), the magnesia content of the final composites could be adjusted from 70.4 to 85.6 vol %. Because the increase in oxide volume associated with the conversion of alumina into magnesia was accommodated by the prior pore volume of the preforms, the composites retained the shapes and dimensions (to within a few percent) of the starting preforms. The MgO/Mg-Al composites were lightweight (2.94–3.30 g/cm3), dense (97.7–99.0% of theoretical), and resistant to hydration. Bar-shaped MgO/Mg-Al composites exhibited average flexural strength and indentation toughness values of 244 MPa and 5.4 MPa · m1/2, respectively.