Rightly or wrongly, for many British people Yoko Ono occupies a dubious place in the Hall of Fame as the woman who broke up the Beatles. Yes, she dabbled in performance art but her star quality resulted from her position as John Lennon’s wife. This is a perception that a major new exhibition seeks to dispel, putting the case that Ono was a key player in the international avant-garde.

Staged at the Museum of Modern Art in Oxford, Have you Seen the Horizon Lately? goes through Ono’s career from the early Sixties until the present day with examples of paintings, photography, installation and film including the famously controversial Bottoms film. But was she then and is she now a serious artist in her own right?

The show starts with pieces from the Sixties when Ono was linked with the Fluxus group. Emphasising the participatory nature of the work and its preoccupation with the ready made and the disposable, the display clearly shows the influence of Dadaism and Duchamp. There are paintings intended for the viewer to colour or to hammer; a step-ladder that had to be climbed so that you could see the word “yes” painted on the ceiling.

Other works trigger not a physical but an imaginative response. Take one of the most successful - “Glass Keys To Open the Skies”. A simple set of keys laid on a small canvas, it invites you to create your own dreams and ponder the nature of painting. The “Instruction Paintings” are similar in vein. Set against musical scores, rarefied texts exhort the viewer to action: “Let water drop on a stone. The painting ends when a hole is drilled.” Conceptual games that hover exasperatingly between the banal and the profound.

First shown in the Lisson Gallery in 1967, “Half A Room” consists of 28 pieces of furniture cut in half and painted white. Regardless of its original meaning, with the passage of time, like a Rachael Whiteread casting, this tired roomset has become peculiarly nostalgic, open to many readings around a sense of loss or absence. It is accompanied by a shelf of empty bottles created by John Lennon. Thirty years on, a bottle labelled “Half A Life” can only add to the potency of the Lennon myth.

Since much of Ono’s work has been done with male collaborators, there is also the suggestion that “Half A Room” may in some way represent herself. A divided self in this case, since her work has consistently, often violently, challenged male authority. The theme is pursued in a new photographic series “Vertical Memory”, featuring a series of the same blurred male features. Changing texts reveal how the image stands in for all the male doctors who have treated or mis-treated Ono at important stages in her life, from her birth to her imagined death.

The overall tone of the exhibition, however, is peaceful, so it is easy to believe the catalogue’s claim that the work is influenced by Zen Buddhism. Partly this is because so many of the pieces are in white, which seems to act like a symbol for purity. It also owes much to two superb installations in the upper galleries. The first - the architectural installation “A-maze” - is again a recreation of an earlier piece. Seeking your path through its transparent plexi-glass walls, you finally reach a toilet in the middle - in full view from the outside. A childish way to shock perhaps, but in a secular age it chimes with the prevailing theme that a voyage of self-discovery may only lead to your own body. Taking up a whole gallery, the final double whammy is nothing short of spectacular: moonbeams are materialised in the form of white nylon ropes diffusing from the ceiling to the ground, where they break over a riverbed, created from small rocks. Nature is invoked as a healer as the viewer is asked to move the pebbles to join those of others in a mound of joy or sorrow.

The opening to the exhibition clearly shows Yoko Ono as a product of her time. Optimistic, idealistic in a golden age of hope, what else are her “keys to the skies” and all-white “non-confrontational chess-board” but artistic versions of flower power? The paradox is that, although her motivations seem to have changed little, in conceptual 1997 they have curious resonances with work that is bang up to the minute. Eat your heart out Damien Hirst. Over 30 years ago Ono was releasing flies into the air and letting apples rot. Now cased in perspex, her historical pieces have curious affinities with the light ironies of Cornelia Parker, whose work is currently on show in the Turner Prize. Clearly, Yoko Ono’s time has come full circle.

Have You Seen the Horizon Lately? is at Moma Oxford (tel: 01865 728608) until March 15 1998. It is accompanied by a wide range of educational events for adults and children, including workshops and family events. A three-session course on conceptual and performance art for sixth-form art students is led by performance artist Marisa Carr. Catalogue at Pounds 9.95 from Cornerhouse Publications: 0161 237 9662