MAYBE IT was only my imagination, but everywhere I looked last Tuesday, people seemed to be yawning. Naturally, I attributed it to the hangover from Monday night's interminable Academy Awards telecast. Shortly after the start of the ceremony, at 10 p.m. Eastern time, Johnny Carson got a big laugh with the line, "Welcome to two hours of sparkling entertainment spread out over a four-hour show." I thought he was joking, too.

Dimly, I recall Oscar shows that were over and done with in two hours. In recent years the event has been taking between two and a half and three hours to limp to a conclusion. This year's procession of announcements, introductions, entrances, recitations, exists and fleeting interludes of entertainment lasted almost 3 hours and 20 minutes, making it a longer test of endurance than the Oscar-winning film, "The Deer Hunter," which ran out of footage at 3 hours, 3 minutes.

Perhaps it was an unwitting form of tribute to "The Deer Hunter," whose will-this-never-end quality seemed an unintentional reminder of the way people felt about the war in Vietnam.

Whatever the cause, there's nothing like a tedious Oscar show to illustrate how much the event can use some cutting and streamlining. Jane Fonda, threatening to degenerate into the Mrs. Miniver of the Hollywood counterculture, accepted her Oscar for "Coming Home" by calling attention to the fact that she'd learned sign language and was demonstrating her facility for "the 14 million handicapped people who cannot share in this ceremony." What could that mean? That Fonda hasn't mastered lip-reading yet? Maybe she'll have a new surprise for us next year.

It was no great privilege to monitor Monday night's service. In all likelihood numbers greater than 14 million nodded off and dropped out before Laurence Oliver and John Wayne made their belated entrances and gave the show a little of the sentimental appeal a vast public might be expected to cherish. Surely Wayne's appearance after his latest recovery from surgery loomed as the single most affecting highlight of the evening. By the time he appeared it was past midnight in the Midwest and 1 a.m. in the East.

Shirley MacLaine, who presented the award to Fonda, took the liberty of telling everyone how proud she was of her "little brother," Warren Beatty, and making a dumb joke about his legendary sex life. While Beatty didn't particularly deserve to win the four Oscars he was nominated for, surely it was humbling enough to go 0-4 in the competition.Why should he have to sit still for an older sister's barbed flattery at this late date? Can't a younger sibling ever escape?

A recuperating old-timer like Wayne may be forgiven slips of the tongue like "Warner Beatty" and "paul Mazurki," especially if you reflect that Warner Baxter and Mike Mazurki may be more real to him than Warrne Beatty and Paul Mazursky, but MacLaine was guilty of deliberate, compulsive misbehavior. Fortunately, Richard Dreyfuss shared the podium with her at the time, and his obvious, bemused awareness of the impulses behind her sisterly presumption helped to put things in perspective.

The evening was haunted by egregious oratory. Very few key participants seemed to have the knack for expressing themselves incisively or knowing when to shut up. More often than not presenters and award-winners alike would get lost down some long, winding verbal trail. I suspect that a time breakdown of this year's show will oblige the producer of next year's Oscar telecast to insist that all speeches be kept short and sweet.

Accepting a screenwriting award, Waldo Salt unreeled the longest sentence since the death of Henry James and never succeeded in salvaging it withe a comprehensible sentiment or, for that matter, an independent clause. Appearing with Ali MacGraw to present the directing award, Francis Coppola took the opportunity to babble about something called "the communications revolution" and then kept scratching his head and beard while vainly searching for words to explain this impending wonder.

MacGraw, who looked terrific and spoke her introductory piece flawlessly, endeared herself for the first time since "Goodbye, Columbus" by staring in disbelief at the fumbling, scratching Coppola. She suggested the classiest girl on campus forced to endure a blind date with the clumsiest bohemian.

Jon Voight's inarticulate ruminations were to be expected; the tales of his rambling, shambling attempts at impromptu public speaking are legend. Coppola's inability to articulate was shocking. He had been splendidly coherent accepting Oscars in 1973 and 1975. Monday night he gave the impression of just returning from a brainwashing session at some inane commune.

Olivier's appearance, touching as it was, also partook of this mindless quality. Accepting his honorary award, Olivier kept a lovely flow of words coming, but they added up to a lullaby of nonsense, vaguely reminiscent of the Shakespearean gibberish that the Beyond the Fringe group used to volley back and forth in one of its best routines. If Coppola seemed fresh from the commune, Olivier seemed fresh off the mothership in "Close Encounters." He sounded like some angelic old party from beyond the stars, bringing greetings to the kind people of Spaceship Earth.

Here is what the greatest living English-speaking actor actually said upon receiving his honorary Oscar from Cary Grant:

"Oh, dear friends, how am I supposed to speak after that? Cary, my dear old friend for many years, from the earliest years of either of us working in this country, thank you for that beautiful citation and the trouble you have taken to make it and for all the warm generosity in it.

"Mr. President, and governors of the Academy, committee members, fellows, my very noble and approved good masters, my colleagues, my friends, my fellow students, in this great firmament of your nation's generosity, this particular choice may perphaps be found by future generations as a title of censure.

"But the mere fact of it, the prodigal, pure human kindness of it, must be seen as a beautiful star in that firmament, which shines upon me at this moment, dazzling me a little, but filling me with warmth and the extraordinary elation, the euphoria that happens to so many of us at the first breath of the majestic glow of a new tomorrow.

"From the top of this moment, in these solid, in these kindly emotions that are charging my sould and my heart at this moment, I thank you for this great gift, which lends me such a very splendid part in this your glorious occasion. Thank you."

The sight of Voight being emotionally overwhelmed by Olivier's word jive was the comic highlight of the show. Poor Voight gets stuck every six words or so, obliging all of us to pitch camp for the night until he thinks of another word to fill the void and can stumble toward the next blank spot in his thought processes. Olivier's nationality and theatrical experience seem to protech him from being at a loss for words, even though the words may not make any sense.

I suppose all the unavailing groping for words might also be interpreted as unwitting homage to "The Deer Hunter,," in which the filmmakers can't find words to express the characters' feelings either and try to do everything pictorially, with results that seem sublimely eloquent to some and maddeningly inadequate or equivocal to the rest of us. Seeing the director, Michael Cimino, may have helped to bring this extremely intellectualized yet emotionally primitive movie into sharper focus. Pudgy, diminutive and evidently very shy, Cimino seemed every bit the disarming, aspiring heroic fantasist, a Walter Mitty who managed to get his heroic mythology on the screen.

The Academy members confirmed their serious pretensions by splitting the major prizes between "The Deer Hunter" and "Coming Home." These films don't stand comparison with the best novels and nonfiction memoirs that have emerged from the war, but in Hollywood they pass for bold, admirable attempts to confront the war and purge its emotional bitterness. In the future the films will probably be thought of as co-winners of the 1978 Oscars, and their equivocal styles of affirmation do seem complementary, the muted reactionary sentimentality of "The Deer Hunter" echoing the muted anitwar polemicism of "Coming Home."

Both films have probably profited from their hazy air of abstraction. The better films derived from novels influenced by the war - "Who'll Stop the Rain" and "Go Tell the Spartans" - were passed by. True to their literary sources, they reflected a corrosive wartime setting that the characters were nowhere near transcending.

It ought to be possible to complete the Oscar show comfortably inside three hours. It would also be a great service in the East if the show started at 9 p.m. Eastern time. AP columnist Bob Thomas suggests eliminating the awards for short subjects and documentaries and cutting the writing awards from two to one. I'm not sure if this is necessary, but it might help to announce the awards for shorts, documentaries and perhaps foreign language film in advance, since they're controlled by select committees of the Academy anyway.

The overnight Nielson ratings indicate significant declines in the last half of the show in both New York and Chicago. It doesn't mean that much to claim an 80 percent share of the audience at 1:30 a.m. If the weekly Nielsens show a good healthy drop from last year's overall rating of 36.3 and 68 percent share of the sets in use, it could be the best thing that ever happened to next year's Oscar show. CAPTION: Illustration, no caption, by Harold Hoover-The Washington Post; Picture, Cary Grant presenting the Oscar to Laurence Oliver.