While also a good portraitist in pastel, Cosio has done abstract paintings in the op art style illusionism. His sculptures are massive blocks of unpolished wood, forming structures which sugest altars for primitive rites. He has been largely influenced by Vasarely and Bridget Riley.
In other works he also drew inspirations from indigenous sources such as the Philippine banig (mat).
He was a prizewinner for five consecutive years in the Art Association of the Philippines (AAP) art competition in 1975-1979; won the grand prize and a British Council study grant in the AAP competition, and a prizewinner in the Baghdad International Art Festival in 1986.