Oliver I. Lay studied painting with Thomas Hicks at the National Academy of Design. He was made an associate of the National Academy in 1870. He is best known as a portrait painter. His diaries are in the collection of the New York Historical Society.
He was related to the Lay family of Old Lyme, Connecticut. His uncle, Oliver Lay, owned a large mill in the Laysville section of town. The artist's father moved to New York before Oliver I. Lay II was born, but the families frequently visited.