This invention relates to a method of preparing a metal-containing amorphous magnesia-alumina-aluminum phosphate catalyst support involving the admixture of an organic cation having a size equal to or greater than 2 Angstroms, the organic cation preferably being a tertiary or a tetraalkylammonium or phosphonium cation, the method permits recovery of a catalyst support having a controlled pore size distribution. The invention also relates to an improved catalytic support as well as an improved petroleum residua upgrading process comprising hydrotreating residua in the presence of the improved catalyst support.