Born in New Alresford 1943 into a Fabian household, Ovenden attended Itchen Grammar School (1954-59) and was taught music privately by Albert Ketelbey. Ovenden was a student at the Royal College of Music, before taking up painting around 1962.
He was tutored by Lord David Cecil and Sir John Betjeman. He attended the Southampton School of Art, and graduated from the Royal College of Art in 1968. One of his most important teachers was James Sellars, an expert on Samuel Palmer.
He moved to Cornwall in 1973 with painter Annie Ovenden and their family. Since then he has been constructing a neo-Gothic building, "Barley Splatt" near Bodmin in Cornwall.
Ovenden was a founder of the Brotherhood of Ruralists in 1975, along with Graham Arnold, Ann Arnold, Sir Peter Blake, David Inshaw, Annie Ovenden and Jann Haworth. The Brotherhood is still extant, although three members have left; in 2005 it had a major London exhibition at the Leicester Galleries. They were given the name "Ruralists" by writer Laurie Lee.