Mary Martin - a hearty laugh, a hearty life

I have news for Tinker Bell: Peter Pan is alive and well in San Francisco. Many people think of Mary Martin as Lt. Nellie Forbush of ''South Pacific,'' the real-life mother of ''Dallas'' star J. R. Ewing (Larry Hagman), or - this year especially - as co-host of ''Over Easy'' (PBS, daily, check local listings for time). But Mary Martin still thinks of herself as Peter Pan.

''I tried to zoom off the garage roof at the age of 5,'' she laughs, a pretty white-haired Peter Pan of a woman with just a little of Tinker Bell in her, too. ''Sure, I flew,'' she adds seriously, with a childlike twinkle in her eye; ''but I didn't stay up in the air very long.''

Now living in San Francisco, where most of ''Over Easy'' is shot, Miss Martin is in New York to make certain you hear about the show, one of PBS's most highly rated daily series. The show, which explores the life styles of mature adults, has featured Hugh Downs and Frank Blair as hosts in the past. Now it has returned for a run of 67 segments with Jim Hartz and Mary Martin as co-hosts. Some of the stars featured are James Stewart, Pearl Bailey, Joel Gray, Bob Hope, and, of course, Larry Hagman.

''Hugh Downs interviewed me and my son, Larry, about two years ago and it was fun. We (Larry and I) talked so much that I was asked to stay on . . . just to finish the sentence! Larry is on one of our shows this year as a guest and I said to him, 'Did you ever in your wildest dreams think, when Hugh Downs interviewed us two years ago, that your mother would be sitting here as co-host interviewing you?'

''He leaned over, patted my hand, and said, 'Thass the way ah arranged it, Momma.' He plays J. R. a little bit.''

Miss Martin, who lived in Brazil for many years until she lost her husband, Richard Halliday, several years ago, has been trying to keep busy so as to overcome the great loss she felt.

Since that time, Miss Martin has done a play with Anthony Quayle, and a television drama. But she keeps busy in many other ways. ''I do not believe in retiring. There is always something you can do. If I didn't do 'Over Easy' I'd be doing something else. I'm doing so much now that I meet myself coming back in airplanes.

''When I finish 'Over Easy,' I go to Washington for a dinner. (Miss Martin is an old friend of the Reagans). I also work for a towel company as their ambassadress, going to different cities, meeting new people. I do benefits in hospitals. I work with little children who can't hear and are learning to speak. Recently, one tiny child who had never made a sound sat on my lap and put her hand on my throat when I sang. Before I left she had made a sound.

''There's so much to do. There are not enough hours in the day as far as I am concerned. I would love to get that across to people. Go out and find them - don't sit back and wait.

''Wake up every morning and say to yourself: 'How many things can I do today?' ''

Does she believe that older people are portrayed properly on TV?

''No. But it is improving lately. 'Over Easy' aims at people beginning with 40 -that's the age people begin to become aware that they are not 20 anymore. But - I played 'Peter Pan' when I was 40!

''In America, age is important to too many people. Not so much in Europe or the Orient. That's wrong. I really hope that there is enough fun and joy in our programs so that people can learn to have a sense of humor about aging.''

Are Brazil and the thousands of acres she and her husband cultivated, not far from Janet Gaynor and her husband, now just a part of her past?

''No. I love Brazil. I don't think I'll live there from now on because it is very sad to go back. Every time I go, I see all the things we planted. It was just a jungle - now it is manicured, like a park. Richard built several waterfalls and planted every conceivable rare plant.

''I had a needlepoint shop in a small town called Anapolis, with one 'n.' We had 12,000 chickens which laid 12,000 eggs every day. We had 200 cows for milk and just about every vegetable there is. It's very lonely not to have Richard there.''

Does she see very much of son Larry? Miss Martin's first marriage, which ended in divorce, came at the age of 16. Larry was raised mostly by her mother. Another child, a daughter named Heller, was fathered by her second husband, producer Richard Halliday.

''Larry came to live with me when he was 12, but that was too late. It made a tremendous mark on the boy's life and on mine.

''During his teen years I was performing all the time and I was the star in the family. He had been used to being the star. I know it's a terrible thing to say, but I felt he was my brother rather than my son. But, now finally, we have found each other and love each other. We never talk about those early days.''

After a long break in their relationship, Larry called his mother in Brazil after his stepfather died and they have been friendly ever since. ''The last eight years together have been fabulous. He is a marvelous father, and his children are a joy for me.''

Is Mary Martin afraid of dominating Larry's six children, as her own mother dominated her child?

''If I lived with my granddaughter, I would just adore her and probably ruin her. But I don't ever want to do that.

''I'm with my grandchildren now more than I was ever with my own children, and it is heaven.'' Does the radiant grandmother have a philosophy she would like to communicate to her ''Over Easy'' viewers?

She crosses her lips with one finger, like a schoolgirl trying to solve a current events question in class. ''Yes, I guess I do have a philosophy.

''Look up, laugh, love, and live. In my lifetime I've done that. I do look up and communicate lovingly with my friend up there . . . although I know God is within. I look up and laugh and live.''

Miss Martin laughs. A hearty laugh. A hearty life.