Yoko Ono - Have You Seen the Horizon Lately?

Museum of Modern Art, Oxford

Aside from supplying Harry Enfield's Self-Righteous Brothers with the best punchline they ever had - "Oi! Ono! No! Oh no, Ono!" - John Lennon's widow has widely been known for ... well, being John Lennon's widow. With the Royal Festival Hall retrospective and this examination of the past 35 years of her art, however, the late Nineties has witnessed a revival of interest in Ono's other career - godmother of conceptual art.

Whatever the dumbfounded Beatles fans may have thought of her notorious bed-ins with the beloved John, the vision of the pair holding court lying naked in white sheets was arguably faithful to one of the most influential art movements of the Sixties. Conceived in her New York loft in 1960, Fluxus, and its free adaptations of Duchamp and the Dadaists, propelled Ono to the forefront of avant-garde art movements the world over. From the perspective of Douglas Gordon's "24-Hour Psycho" and Rachel Whiteread's inside-out "House", it's apparent that Ono anticipated the arch conceptual games so fashionable in contemporary art. The Oxford MOMA exhibition includes, for instance, Ono's "Half-a-room" environment from the Sixties - who would bat an eyelid today at a domestic interior whose furniture and objects are cut in half and painted white?

Damien Hirst, though, has had it a lot easier than the 64-year-old Japanese banker's daughter. The erroneous belief that Ono was responsible for the break-up of the Beatles was merely one manifestation of the antipathy reserved for Ono and her work through the Sixties and Seventies. The stoicism with which she has weathered her isolation is nowhere more apparent than in "Portrait of Nora" (see picture). The pixillated self-portrait is part of a wider conceptual photographic examination of female relationships with male power that she has been undertaking through the Nineties.

Inevitably, Ono's earlier work will attract most attention for its parallels with today's Brit-artists, but if she resents this irony, Mrs Lennon isn't showing it: "I wish John could have known all this would happen," she has said. "He would have loved it."

To 15 March, Museum of Modern Art, 30 Pembroke Street, Oxford (01865 722 733)