Warmhearted revival for O'Neill's only comedy;

Ah, Wilderness! Comedy by Eugene O'Neill. Starring Philip Bosco, Dody Goodman. Directed by John Stix.

What better season than the good old summertime to revive Eugene O'Neill's only major comedy. And what an attractive revival this warmhearted, warm-weather celebration of love and independence is receiving at the Haft Theater on West 27 th Street.

The new version of ''Ah, Wilderness!'' is being described as the 50 th-anniversary production, recalling the fact that the play first opened on Broadway in 1933. Whatever the designation, the Roundabout Theatre Company displays both freshness and a due respect for the nostalgia with which O'Neill remembered a time from his own boyhood.

The action of ''Ah, Wilderness!'' takes place in a small Connecticut town during the two days that begin with the morning of July 4, 1906. It is a day of firecrackers, beach outings, picnics, and a climactic lobster dinner at the home of newspaper publisher Nat Miller and his family. Naturally the Glorious Fourth turns out to be somewhat less glorious than those concerned had hoped. Most of its troubles spring from the ultimatum delivered by dry-goods store owner David McComber to Nat. McComber is outraged at the kind of love letters young Richard Miller has been writing to pretty Muriel McComber.

The irate McComber berates Nat and delivers a note in which Muriel breaks off with Richard. Not until later is she able to explain to her dejected suitor that the letter was written under duress. By then, a certain amount of damage has been done. But because ''Ah, Wilderness!'' reflects O'Neill in one of his rare sunny moods, the damage is not irreparable.

The Miller family's memorable Fourth of July moves with savored leisureliness through crises, domestic comedy, and misadventures to its final happy resolutions. In the course of its unfoldment, O'Neill wrote a series of what have almost come to be set pieces for actors. The Roundabout Theatre Company cast responds to these opportunities with appreciative zest and overall affection.

Philip Bosco's Nat Miller combines paternal authority and wise tolerance in equal measure. He is in every respect a benignly substantial presence. As Mrs. Miller, the delightful Dody Goodman presents a wife and mother whose reflexes are as conventionally conditioned as her devotion to her family is unconditional.

Scott Burkholder gives a mettled and sensitive performance as the romantically headstrong rebel with several causes and a head full of quotes from such scandalous authors as Wilde, Shaw, and Ibsen. Liane Langland's Muriel realizes the inner strengths of an outwardly timid girl, a heroine to which a boy like Richard would be faithful and true.

In the roles of the star-crossed Uncle Sid and the spinster Aunt Lily, Robert Nichols and Laurinda Barrett convey the melancholy and sadness that underlie what is first portrayed as a comic romance. On the other hand, the autumnal domestic happiness of Nat and Essie and the youthful raptures of Richard and Muriel create the essence of the mood summed up by Nat when he observes quietly: ''From all reports, we seem to be completely surrounded by love.''

It is this sense of natural and decent affection which permeates the production staged by John Stix. At the preview I attended, the performance began somewhat uncertainly but gained in strength and conviction as the evening progressed. Besides those already mentioned, the cast includes John Dukakis as Yale-bound Arthur Miller, Kelly Wolf as Mildred Miller, Mark Scott Newman as little Tommy Miller, and Joseph Leon as Muriel's fuming papa.

Designer Kenneth Foy has made a virtue of necessity by situating the Millers' comfortable living-dining room between the tavern and harbor settings of the second act. The revival was lighted by Ron Wallace (apparently on a low budget) and costumed picturesquely by Gene K. Lakin. Philip Campanella's choice of incidental music runs to period favorites and a spot of ragtime. Very nice.