The configuration and ornamentation of the Bascones altarpiece corresponds to Early Renaissance Castilian style. It has a sotobanco, predella, two main sections and a wide frontispiece or attic flanked by two triangular gables and a mixtilinear centre gable crowned with a niche and bust. Decorative representations of the Sun and Moon are scattered between the gables. The entire attic stands under a large, slightly pointed arch. The altarpiece is divided vertically into five main sections, the central one of which is slightly broader than the others.
Vertical sections are limited by columns of Corinthian order whose shafts are decorated a candelieri with typical Plateresque motifs of goblets, cherubim, masks, busts, climbing plants and grottos. The same motifs also appear on the bases of columns and entablatures. Panels forming the sides and backdrops of compartments are decorated with typical Plateresque motifs of goblets, cherubim, masks, climbing plants and grottos. The upper part of friezes is decorated with a scallop shell motif.