A composition and process for removing photoresist and/or sacrificial anti-reflective coating (SARC) materials from a substrate having such material(s) thereon. The composition includes a base component, such as a quaternary ammonium base in combination with an alkali or alkaline earth base, or alternatively a strong base in combination with an oxidant. The composition may be utilized in aqueous medium, e.g., with chelator, surfactant, and/or co-solvent species, to achieve high-efficiency removal of photoresist and/or SARC materials in the manufacture of integrated circuitry, without adverse effect on metal species on the substrate, such as copper, aluminum and/or cobalt alloys, and without damage to SiOC-based dielectric materials employed in the semiconductor architecture.