It is the heraldic device of the Grace family, and it sits flanked by two Latin inscriptions in raised black-letter script, one of them dated 1543. The doorway itself is layered with Tudor roses, vine-leaf and grape motifs, crocket pinnacles, and triangular pilasters, an unusual concentration of decorative stonework for what is, in structural terms, a modest chapel addition in a country graveyard. A somewhat clumsy hood-moulding added by the Office of Public Works now shelters the whole composition, a practical intervention that sits at odds with the carving beneath it.

The church at Tullaroan, dedicated to Our Lady of the Assumption, sits on a natural ridge in undulating pasture land, with a public road running past the western wall of its rectangular graveyard. The building is a nave-and-chancel plan, oriented roughly east to west, and the oldest surviving fabric belongs to the chancel, which retains a 13th-century double cinquefoil sedilia, the carved stone seating recessed into the wall where clergy would sit during parts of the liturgy. The wall dividing nave from chancel carries a 15th-century chancel arch alongside a single-light ogee-headed window. Much of the church has not survived; only the original south wall of the chancel, the dividing wall, and the north wall of the nave remain standing. The south chapel was added in 1543 by the Grace family, with Sir John Grace associated with its construction. Its windows include a two-light elliptical-headed opening in the south gable, ogee-headed lights in the east wall, and a quatrefoil window at the very apex of the south gable, still showing the holes where glazing bars were once fixed. The chapel and church are built of roughly coursed limestone and sandstone rubble, and several graveslabs and chest tombs within the graveyard are closely associated with the site.