Grevillea rubiginosa is an open tree or shrub which can grow up to tall in sheltered areas and in open habitats. Its leaves are long and wide with a red indumentum on the underside. The conflorescence is much-branched and the floral rachis has distinctive reddish hairs. The perianth is oblong-ovoid in shape, long, wide and hairy on the external surface. The pistil is long and glabrous. Both the perianth and style are creamy-white. The fruit is a follicle long and wide that is smooth and in an oblique position on the pedicel. Flowering occurs between May and January, usually flowering later in higher altitudes.
Taxonomy
This species was formerly regarded as a subspecies of Grevillea exul. The specific epithet is derived from the Latin rubiginosis, meaning "rusty red" in reference to the red or brown hairs on the floral rachis.