CAN A family man make a living as a Washington actor?

Few do, but Robert Prosky, in his 20th season at Arena Stage, has and wouldn't want it any other way.

Prosky has a working wife and three sons, and he says that he couldn't have gotten ahead as an actor without the solidity of family life. "I know myself, and my sane, wonderful family life is my rock."

You see Prosky other places than at Arena, where he's played over 150 roles since he made his bow in "The Front Page" at the start of the '58-'59 season. He was handling cash on the cover of last month's Washingtonian magazine. You've seen him touting Perpetual Savings & Loan and Safeway Stores on TV. He does TV voice-overs and radio commercials. He made a TV series for children one summer in Boston ("and I still get about $16 a month on reruns!"). He was in the short-lived "Beacon Hill" and several other teleplays.

In short, Prosky hustles.

"But," he adds, "Arena comes first. The danger is in becoming a bookkeeper-type actor or a commuter. I've avoided such temptations, because though part of me is the family man, an equal part is actor - and that's what my life has been about."

Now in previews for Brecht's "The Caucasian Chalk Circle," Prosky opens Wednesday night in a role he's always wanted to play: Azdak, the drunk who becomes a wise judge. It's a major part for any actor, and there's an added dimension. When the same play became the opening production for Arena's third home and David Hurst was Azdak, Prosky did a half-dozen minor parts.

"What I've learned in those 17 years!" Prosky sighs. "I had a heavy, show-off technique and I now know I didn't really know much about acting. What I did know, felt, was that to act you've got to do it, act every night, every week, all the time."

Those who've watched him will agree that Prosky has come a long way in his craft. At first, he had the interest any unfamiliar player commands. Then, for some years, I began to think Prosky was the deadliest, most predictable actor alive. He seemed to grind on and on and on, always the heaviest character man unable to lick those long exits that are a built-in challenge of arena-style staging. I'd sigh with relief once he had lumbered out of sight.

Gradually something happened. Prosky is convinced now that he "began to learn about acting" with his casting as an old clown in "He Who Gets Slapped." He recalls it vividly: "It was a small part, but I got so interested in the guy, so involved. I got so I knew all about him, his thoughts, his walk, how he'd break up tricky dialogue. To me that study was my career breakthrough."

His 1965 clown was followed by better roles in "The Iceman Cometh," "You Can't Take It With You" and "An Enemy of the People," a plateau against but on a more resourceful level.

It seemed to me that I saw a new Prosky as the landlord of "Moonchildren" in the '71-'72 season. It was a deeper, more relaxed approach. Rewarding parts came along, the stage manager of "Our Town" and, his most challenging role, Willy Loman in "Death of a Salesman."

Willy is a deceptive part, and Lee Cobb set a standard few actors seem to have analyzed. Cobb's Willy was, immediately and throughout, exhausted. This requires a curious kind of energy to sustain; and from his baggy pants, his slouch and sagging shoulders, Prosky sustained that essence. I've seen more noted actors get so lost in the passion of the man that they forgot Willy's essence: a worn, burned-out man.

Another worn figure whom Prosky depicted with a kind of last-spurt bluff was his Matthew Brady (or "Williams Jennings Bryan") of "Inherit the Wind," the Lawrence and Lee dramatization of the Scopes trial. Prosky played this in repertory with "Our Town," preparing for the Soviet Union tour in 1974 and convincing me that he was an actor to respect.

The Russians felt the same way. As a result of those two roles in Moscow and Leningrad, Prosky is, to the Russians, "a great American actor," more known to them than any of his more famous contemporaries here.

In Philadelphia's amateur group, the Academy Players, Prosky's picture shares lobby space with another, more famous, former member, Grace Kelly. "No, I wasn't there in her time; but when I acted there, she was the company's most admired graduate.

"I was born in Philadelphia in 1930. I did my first acting in Roxborough High School, where my hair turned gray in my teens. That was just right to play the 'Our Town' stage manager, a part I completed full circle in Moscow. I went on to Temple University as an economics major, expecting to follow my father in his grocery business. On the side, I did two plays there, then completed my Army service.

"Then came a few months of great change. At my father's death, my mother recognized that I, their only child, wasn't much interested in the grocery business. She encouraged me to apply when Michael Ellis held auditions in a talent hunt, the winner to get a part at his Bucks County Playhouse. My winning cast me with Walter Matthau and William Windom in a play directed by Ezra Stone.

"Ezra - radio's Henry Aldrich - was great to me and encouraged me to try for a scholarship at the Theater Wing, which I won. I spent two or three years kicking around the New York scene, doing mainly summer stock. Then I connected with Arena."

It was in his early years at Arena, in its Old Vat period, that Prosky met his wife, Ida, then working on The Washington Post, a tiny, wren-like opposite of her full-bodied husband. Within a few years came Stefan, now 16; John, 15, and Andy, 12.

With five mouths to feed, Prosky took what extra jobs could be fitted into his schedule. They bought a house on Capitol Hill, later a second. As a Philadelphian, Prosky naturally gravitated to its longtime summer resort, Cape May, where the family holidays while Dad treks to New York for whatever summer work his agent lines up.

Cape May inspired a typical Prosky response: "On a straight line it's no distance, but drive by road and you quadruple it, so I took flying lessons and shared a lease on a plane."

Most of those years Ida Prosky was a homebody, but with the boys settled in school, she took on a job with the Capitol Hill Day School to direct special programs. Last winter, for instance, she cooked up a novel way for 5-and 6-year-olds to celebrate Lincoln's birthday. They brought him a birthday cake and lit its candles before his Lincoln Memorial statue.

Stefan plays the oboe, John goes to a school where an instructor recently turned "The Zoo Story" from a two-to a four-character play with a part for John, and Andy will have a small role in Arena's Brecht.

"I'm not saying every actor would have a family life as a top priority, but for me I have to. And though the agents assure me I could get more money and fame by working other places, I know I couldn't be satisfied with all that leaping around."

The odds are tough, but Prosky and a few others have proved that it's possible for a family man to be a Washington-based actor. This kind of life is beginning to be possible in other parts of America. Not so long ago it was all but inconceivable anywhere other than New York, Los Angeles or, of all places, the Cleveland Play House.