By JOHN J. O'CONNOR Think a moment - on which television outlets did you first see the following productions: Katharine Hepburn in ''The Glass Menagerie,'' Laurence Olivier in ''The Merchant of Venice,'' Carol Burnett in ''Friendly Fire,'' Colleen Dewhurst in ''The Women's Room,'' Christopher Plummer in ''Cyrano de Bergerac,'' Julie Harris in ''The Little Moon of Alban,'' Henry Fonda in ''Gideon's Trumpet'' and Alfred Lunt and Lynn Fontanne in ''The Magnificent Yankee''?
Public television? Cable, of either the standard or pay variety? No, all of these distinguished programs could be found during prime time on the commercial networks, the first four on the series labeled ABC Theater and the rest on the Hallmark Hall of Fame. This reminder that the networks can lay claim to not-infrequent bursts of outstanding quality - a fact that is being curiously downplayed by some advocates for the newer technologies - is prompted by two developments: the Museum of Broadcasting's current tribute, running through April 18, to the Hallmark Hall of Fame; and the ABC Theater presentation tomorrow night at 9 of ''Consenting Adult,'' starring Marlo Thomas and Martin Sheen as the parents of a college-age athlete son who suddenly announces that he is a homosexual.
Hallmark's involvement with broadcasting began in the 1930's when Joyce C. Hall, founder of Hallmark Cards, decided that radio could provide an effective and classy sales vehicle. The company came to television in 1951 and that year sponsored the first opera created for television, Gian Carlo Menotti's ''Amahl and the Night Visitors.'' Under the supervision of Albert McCleery, the Hallmark programs began to command attention with such unusual fare as Maurice Evans in ''G.I. Hamlet,'' a version of Shakespeare's play designed for servicemen during World War II. Then, in 1955, George Schaefer, the producer/director, and Mildred Freed Alberg, the executive producer, entered into a Hallmark collaboration that would employ an enviable degree of artistic freedom for much of the next 15 years.
At a recent seminar at the Museum of Broadcasting, Mr. Schaefer, still very active and still fighting the good fight to respect the assorted talents of writers and actors, recalled the luxury of having complete artistic control in the days before networks began to interfere with their silly notions of ''high concept'' and the like. For a 90- minute show, Mr. Schaefer was able to give his cast 15 days of rehearsal. At the same session, Teresa Wright, the fine actress who appeared in Hallmark's production of Shaw's ''Devil's Disciple,'' spoke about the extended rehearsals having allowed her to work toward ''the playwright's truth.''
The ''Schaefer years'' certainly have their abundance of outstanding credits, from ''The Green Pastures'' with William Warfield and Earle Hyman to ''The Lark'' with Julie Harris, Boris Karloff and Basil Rathbone; from ''The Tempest'' with Maurice Evans and Richard Burton to ''The Fantasticks'' with Ricardo Montalban and Bert Lahr. And the list of highly successful Hallmark presentations after 1970 includes George C. Scott in ''Beauty and the Beast,'' Alec Guinness and Genevieve Bujold in ''Caesar and Cleopatra,'' and Richard Thomas in ''All Quiet on the Western Front.'' The record, establishing what the company calls ''a tradition of excellence,'' speaks for itself. Coming this Tuesday evening at 9 on CBS is ''The Corsican Brothers,'' a Norman Rosemont Production that, if nothing else, is bound to be opulent.
On the face of it, ABC Theater has been more of a programming grabbag, filled with everything from modest efforts by new writers (''The Last Tenant'' and ''Benny's Place'') to full-scale major productions (''Eleanor and Franklin'' and, first among the ''docudramas,'' ''The Missiles of October''). It has offered ''event TV'' such as ''The Day After,'' ''problem TV'' such as ''Something About Amelia,'' and adaptations of stage plays such as ''Wedding Band,'' ''The Shadow Box'' and ''The Elephant Man.'' The connecting thread is that the mere presence of the label ABC Theater connotes something beyond the ordinary. Brandon Stoddard, now the president of ABC Motion Pictures (a position also responsible for theatrical releases like ''Silkwood'' and ''The Flamingo Kid''), has explained: ''ABC Theater seeks to present a handful of television movies each year purely on the basis of quality and importance, with no commercial considerations.'' Tomorrow's ''Consenting Adult'' happens to be the 50th presentation in a truly remarkable record that began in December 1972 with ''If You Give a Dance You Gotta Pay the Band.''
''Consenting Adult'' is not the most impressive of ABC Theater presentations, but, courtesy of a thoughtful production and an exceptional cast, it is a film that commands attention. Based on the novel of the same name by Laura Z. Hobson (''Gentleman's Agreement''), John McGreevey's script is just a trifle too pat, touching on most of the cogent points but leaving no room for surprises. Ken and Tess Lynn (Mr. Sheen and Miss Thomas) are pleasant, well-meaning people living a decidedly upscale life. He is just recovering from a heart attack and she is coping sympathetically when their only son Jeff (Barry Tubb), a star collegiate swimmer, decides to announce his homosexuality. The situation is carefully calculated in dramatic terms. In fact, Jeff has never had sexual relations of any sort, but he believes he is attracted to men because that's what his fantasies are about. His mother, hoping to change matters, sends him to a psychiatrist who claims that 25 percent of his ''highly motivated'' patients have switched from homosexual to heterosexual inclinations. Jeff's father is so angry about his son's revelation that he refuses to deal with him at all, reverting to the standard stereotypical comments about ''fags'' and ''queers.'' Only Jeff's sister and her husband offer the unhappy young man unstinting support.
On a certain level, ''Consenting Adult'' is almost as chaste as ''That Certain Summer,'' the groundbreaking TV movie about homosexuality that was carried on ABC in the early 1970's and which also starred Martin Sheen, that time playing one of the homosexual lovers. Jeff is not flamboyant or ''different'' in any way that might be considered unsettling in ''polite society.'' But he is an attractive vehicle for making a broader point. The 84-year- old Miss Hobson has underlined her purpose: ''I believe that thousands of young people who are still in agony over their discovery that they are homosexual will see this picture and realize they must stop being ashamed. This film says to them, 'Don't let society brainwash you into staying in the closet. Tell your parents now. Sure, there will be trouble, but you'll live through it, and it's always better to be honest in the end.'' This is still not likely to be a terribly welcome or popular message in today's supposedly liberated world, but ABC Theater delivers it with an admirable combination of emotional clout and dignity. The superb performances of Miss Thomas, Mr. Sheen and Mr. Tubb make this Starger Company Presentation, directed by Gilbert Cates and produced by Ray Aghayan and David Lawrence, the kind of small movie that is likely to have enormous reverberations.
Anybody who works in the ferociously scrambling world of television will concede that it is almost miraculous that anything of value ever gets produced. But, against formidable odds, it does. ABC's Mr. Stoddard can still get as excited as a frisky teen-ager when discussing his various projects. At the moment, he is in the script-development stage of an ABC Novel for Televison that will cover America's involvement in a war - in Vietnam and at home - during the 1960's and 70's. The writer is John Sacret Young (''Rumor of War,'' ''Testament''). ''The Black Rainbow,'' dealing with three generations in a single fictional family, is expected to run between 10 and 14 hours.
Clearly, in terms of indisputable quality, however scattered and sporadic, commercial television can still be ambitious and, more significant for the new programming entities, highly competitive.
