A lavish, exuberant season at the Oregon Shakespearean Festival

During the 1960s and '70s, the United States experienced an exuberant rejuvenation of its theater. The stranglehold of Broadway was broken as dozens of companies sprouted like mushrooms in the hinterlands. The fear that the future would be found only on television abated, as attendance figures for live theater shot up. Playwrights such as Sam Shepard, David Mamet, and Robert Patrick were able to establish national reputations by means of local productions.

This renaissance went forward largely under the banner of the ''regional repertory company,'' with equal emphasis placed on all three words. To many, it became an article of faith that a company of players, establishing an identity and honing ensemble skills while performing a body of work for a regional audience, was the salvation of the theater.

The era of expansion may be over, or it may simply be dormant, awaiting a change in economic fortunes. In either case, the ''regional'' legacy of the revolution persists. Although theater has had its recession victims, there survives a strong grass-roots network of local theaters, many of them producing original and creative work, some of them actively pursuing the ideal of reflecting a ''regional'' character.

But two-thirds of the formula - the ''repertory company'' - has been jettisoned or pared back by a great many regional theaters. Companies that hire a fixed group of actors to perform a season, and maintain a number of plays in production at any given time, are becoming few and far between.

Even those struggling to keep the banner aloft have for the most part made strategic retreats, cutting back on the acting corps and producing small-cast, single-set pieces.

In this context, the lavish, exuberant, confident productions of difficult works being staged by the Oregon Shakespearean Festival here takes on a special significance. Over the current season, the Oregon festival will have staged 12 plays, with as many as nine running at any given time.

The festival has in its employ more than 60 performers, about 20 of them members of Actors' Equity. This makes the Ashland organization the largest employer of actors in the country in terms of annual ''actor-weeks.'' In an era increasingly dominated by the six-character, one-set situation drama, the ''regional repertory company'' flame burns all the more brightly in this rural corner of Oregon.

None of this would be worth recounting if the festival's offerings weren't worth the long journey most audience members make from San Francisco or Seattle. But its current season is one of which any company, ''regional repertory'' or otherwise, could be proud.

The festival has on occasion produced seasons more notable for their ambition and technical flourish than their artistic achievement. But theatrical pilgrims making the trek to the foothills of the Siskiyous this year will be challenged and rewarded by a series of intriguing productions.

Shakespearean plays in the outdoor theater include ''Much Ado About Nothing, '' ''Richard III,'' ''Cymbeline,'' and ''Hamlet.''

A company whose reputation is founded on Shakespeare will naturally be judged most stringently on the latter. Some traditionalists won't be happy with Robert Benedetti's current version, but for the most part it will withstand the scrutiny very well.

Whether as a deliberate directorial choice, or simply as the effect of his casting, Benedetti has staged the lightest ''Hamlet'' you are likely to see (an opinion based on a preview seen a few months ago). It is all too frequently unnoticed, but ''Hamlet'' is a very funny play - there is a great deal of black humor lurking just beneath the angst. This facet of Shakespeare's prismatic masterwork is revealed more clearly in the Ashland production than in any other I have seen.

The major weakness and compensating strength of the production I saw are both grounded in the performance of Mark Murphey, the actor in the title role. Murphey has an extraordinarily light touch with this dark prince. His Hamlet seems more troubled than tormented, more earnest than obsessed, and as a result some of the fire and intensity is lost.

What we get instead is a Hamlet who is believably human and downright likable , a fundamentally decent person too put off by the world to adapt to it but brave and cheerful in extremity. In this production, for once, Hamlet's ''mad'' scenes are genuinely funny. For once, his friendship with Horatio (sympathetically played by Allen Nause) seems warm and real. For once, it is possible to believe that Hamlet really is well loved by the Danish people.

The rest of the cast plays with similar plausibility. Richard Elmore's Polonius is funny, and yet Elmore has the wit not to make him an utter fool; in his hands, the old man retains enough human dignity that his death is affecting. Denis Arndt's Claudius, for all his treachery, comes across as a competent and capable ruler. Megan Cole is a strong and sensual Gertrude. Gayle Bellows's Ophelia suits Murphey's Hamlet - not really heartbreaking, but clear and charming.