"I don't know how they eat this stuff," said Rep. Ted Weiss (D-N.Y.), manfully attacking an enormous slice of barbecued beef and (with a golden Big Apple pin in his lapel) looking very much like he was: a New Yorker at a Texas party.

As he struggled to subdue the barbecue without the aid of a knife, Weiss pondered a stylistic note on Washington parties: "We have groups visiting from New York all the time, but no parties like this. We'll have to start doing something to keep up our reputation."

On the other side of the caucus room in the Cannon House Office Building, a seven-man band called the B. D. Griffin Democrats was playing tunes like "Sweet Georgia Brown," "Yellow Rose of Texas" and San Antonio Rose" with a strong Texas swing flavor, and a few couples were dancing in the old style, where the couples get close together and hold hands.

The party, hosted by House Majority Leader Jim Wright (D-Tex.), was a reception for 62 members of the Fort Worth Civic Leaders Association, 62 of whom arrived here Sunday and leave tonight after a bit of sightseeing and briefing sessions with staff people from the White House, Congress and the Pentagon. The guests of honor were outnumbered about 10-to-1 by Washingtonians, including more than a dozen congressmen and a whole flotilla of Air Force generals and colonels.

Host Wright, wearing a necktie spangled with tiny Lone Star flags circulated casually but efficiently through the big room, shaking hands with friends and constituents and smiling warmly for the ever-present cameras. "I'm starting a Wright-for President drive," confided admirer Mike Jackson. "Don't saddle me with that," pleaded wright."I have enough problems already."

"I became a citizen last year," said Jackson, a native of Germany, "and Congressman Wright sent me a telegram of congratulations and a flag that had flown over the U. S. Capitol. I have it on a 50-foot flagpole outside my business, now."

This is the third consecutive year the Fort Worth group, made up of elected officials, business leaders and members of the Chamber of Commerce, has visited Washington, and the trip (which began with 40 people in 1977) becomes more popular each year. "They don't come to ask for anything," said Wright, a slight tinge of amazement in his voice, "but just to say 'thank you' to their public servants. They cook up all this chili and barbecue down in Texas and fly it up here, and I'm very glad to see it. The two things a Texan misses most in this town are barbecue and Mexican food."

Gene Wood, president of the Civic Leaders Association, noted proudly that they had flown in 400 pounds of barbecue, 200 of beans, 200 of chili and 150 cases of Coors beer with "very little left over." Coors seemed the fastest-moving item at the three bars, with Jack Daniels holding a comfortable lead in the hard-liquor line.

But it wasn't all partying. "These people really came to be informed," said Air Force Capt. Iris Galan, who arranged some of their Pentagon briefings. "They're a very sophisticated group, too. They knew just what questions to ask." CAPTION: Picture, Rep. Jim Wright; by James A. Parcell -- The Washington Post