Brothers Steve and Chip Baird, who learned the subleties of platform tennis locally when their father, former Undersecretary of the Navy Charles F. Baird, was based in Washington during the Johnson Administration, won the Passport Scotch Platform Tennis Playoffs yesterday at Columbia Country Club.

The polished and personable brothers thrashed Rick Swift and New Canaan, Conn., and patriotically named John Adams of Philadelphia, 6-0, 6-4, in the morning semifinals. They were equally businesslike after lunch, routing Dill Ayres of New York and Craig Mielke of Darien, Conn., 6-3, 6-1, 6-1, to capture the $2,200 first prize.

Bill Morris, a real estate man from Bethesda, and Ted Prince, a Chevy Chase attorney, won the Middle Atlantic Championship, an amateur event played alongside the pro-tournament. They beat brothers Burke and Jeff Hayes of Bethesda in the final, 4-6, 6-3, 6-4.

It was a perfect day for platform tennis - which is to say, no one was frostbitten. About 250 spectators well insulated by layers of clothing and further warmed by blankets and beverages, turned out on a clear, brisk, almost windless afternoon to watch the local showcase of an interesting country club sport that is gradually going public.

An outdoor, winter sport started 50 years ago in Searsdale, N.Y., platform tennis is played on the 44-by-20-fot court, painted on a deck of wood or metal, surrounded by a 12-foot wire fence.

Equipped with short-handled, perforated wooden paddles, players hit a sponge rubber ball over a net in a game similar to tennis, except that shots are played "off the screen," in the manner of squash. This makes for long rallies and all kinds of intriguing geometric and strategic possibilities as teams maneuver for all-important command of the net.

Scoring is the same as in tennis, but only one serve is allowed. Because serves may also be played "off the screen," service is not as great a weapon as the ability to play a series of shots that set up a dominating position at the net.

"Steve and I never had strong serves, but we've always been good at breaking serve. That's what happened today. We were creaming the ball on the return of serve," said Chip Baird, 25, a five-time national junior (under 21) champion who is a first-year graduate student at Harvard Business School.

The Bairds were exposed to the platform tennis as youngsters in Chappaqua, N.Y. Their father has played the game for 20 years, and he started them in at about 10 years ago. Chip and Steve, now 27 and a personnel manager for Citibank in New York City, learned the game at the Chevy Chase Club in 1966-69, when their father was working out of the Pentagon, and have since combined it with tennis (Steve played four years on the varsity at Bucknell, Chip three years at Harvard.)

"They have an unusual amount of patience for young players. They wait out their openings and then apply the power," said Papa Baird, now the president of International Nickel.

He also played in the tournament and at least knew that he had lost to a superior team. His sons did in. Baird and partner Roger Lankenu of Chapaqua in the second round, 6-1, 6-2.

"Four years ago, we played them in the final of the Middle Atlantic here, and they beat us, 6-4, 6-3, 6-2." Papa Baird said, not sounding at all as if someone had stolen his porridge. "They've improved an awful lot and have just gotten out of our league."

Chip admitted that he was "just lucky" to be in the tournament at all. Getting to Washington from snowbound Cambridge, Mass., was something of an adventure.

When he set out on Thursday afternoon with his wife of six weeks, Jane, not even mail carriers were making their appointed rounds. Hardly man nor beast was able to buck the drifting snow and chilling winds.

"All flights had been canceled, the governor had declared a state of emergency, and people were supposed to stay in their homes. Unnecessary driving was subject to a $500 fine and impoundment of the car," he recalled yesterday.

"I have a little Alfa Romeo, and I couldn't even see it under the snow," he added. "So my wife and I stuffed a knapsack and two duffle bags - I was optimistic, and packed five changes of clothes with my paddle gear - and walked 2 1/2 miles to the MBTA (subway) at Harvard Square."

They got to South Station in time to catch a train for New York, a trip that took 6 1/2 hours. They grabbed a few hours of sleep at Steve's apartment in Manhattan, caught another train out to their parents' house in Short Hills, N.J. Friday morning, and drove with Mr. Baird to Washington.

It all seemed worthwhile yesterday, as the Bairds savored their first triumph on the six-tournament, $142,000 Passport Circuit.

They remain in third place in overall point standings, behind Herb Fitz-Gibbob-Hank Irvine (who withdrew here after FitzGibbon injured his hand) and Clark Graebner-Doug Russell (quarterfinal losers to Ayres and Mielke), going into the $50,000 circuit finale at South orange, N.J., next month.

Ayres, who also works at Citibank and Mielke, a tennis pro, upset John Brownlow of Cleveland and Scott Rogers of Rye, N.Y., in the semis, 6-1, 0-6, 6-4, but had little left for their first final.

They were in the match only briefly in the first set, breaking Chip Baird to get back to 3-4. But Ayres immediately lost his serve, foot faulting to 30-40 and watching forlornly as Mielke punched a forehand volley long, unforced.

Steve Baird served out the set at love, and the brothers rolled from there, returning serve ferociously and keeping on constant pressure. Steve Baird's play off the screen was simply spectacular, and both players combined restraint and aggressiveness in a way that did their father's tutelage proud.