Oppé was the Deputy Director of the Victoria & Albert Museum 1910-1913 and a founder member of the Walpole Society. He began collecting English watercolours in 1904. By his death his collection comprised 3,000 drawings, oil sketches and prints ranging from the 17th to the 20th century. It included 27 drawings by Richard Wilson and two attributed to him. Most of Oppé's distinguished collection is now at Tate, London, which, following the death of his son, Denys Oppé, acquired it in 1996 with the assistance of the Heritage Lottery Fund and the National Art Collections Fund (now Art Fund). See further:Lyles & Hamlyn 1997