Americans embraced Christmas by feeding the homeless, giving toys to needy children and praying for U.S. hostages in Lebanon and the families of victims killed in the crash of a jetliner in Scotland.

President Reagan asked the nation to say "a special prayer this Christmas" for those who lost loved ones in the crash of Pan Am Flight 103 that killed all 258 passengers, most of them Americans returning home for Christmas.At a housing project in New York City, a group of Wall Street traders Saturday watched their yuletide spirit brighten the faces of hundreds of poor families who were given a take-home Christmas feast - a $100 pre-cooked turkey dinner big enough to feed eight people.

"It gives me a tremendously great feeling to help out people who are less fortunate than I am," said Mark Feely, 34, while handing out the boxed dinners containing a 16-pound roast turkey, stuffing, gravy, sweet potatoes, string beans, cranberry sauce and pumpkin pie.

Some 1,000 free turkey meals and about 600 food baskets for the homeless were paid for with a $150,000 contribution from traders on the New York Stock Exchange.

"I lost my job about a month ago, and it's getting kind of hard," said Simon Sumpfer, an unemployed construction worker with three children. "This makes me very happy. Merry Christmas."

In Manchester, New Hampshire's largest homeless shelter, New Horizons, cooked up a Christmas Eve turkey dinner for residents occupying its 70 beds. Shelter officials said it will let holiday visitors sleep in Christmas morning instead of enforcing the usual 8 a.m. wake-up call.

"A lot of them are out of work," said Jack Provost, the shelter's program director. "When they can participate in it, they feel they do belong in the culture."

In San Francisco, hundreds of homeless people planned Christmas celebrations amid their jumble of sleeping bags, bicycles and shopping carts at the glittering Civic Center Plaza.

"I'll spend Christmas right here," said David Quinn, 32, who last worked three years ago as a cook. "I'll light a candle. I'll sing Christmas songs. I'll cry a little."

Some of the homeless men and women put up a Christmas tree at their makeshift camp in the shadow of City Hall. "This is our corner. This is where we live," said William Keck, 25, who lost his part-time construction job three months ago.

More than 2,500 people were fed by some of San Francisco's fanciest restaurants and given expensive clothes from designer shops Saturday after poor women and children modeled thousands of dollars of new apparel at a fashion show put on by the social activist Glide Memorial Methodist Church.

"I've been here for 25 years doing a lot of programs for poor folks, but something like this is real special," said the Rev. Cecil Williams, who organized the Christmas Eve program at the church. "It helps them to see themselves as beautiful people.

In Houston, nearly 400 needy Hispanic children thought they would not have a merry Christmas after thieves broke into the office of the Mutual Society of Mexican Workmen and stole nearly all of the 1,500 toys the volunteers collected the last three months. But the Mexican Workmen solicited last-minute donations and were able to replace the stolen toys.

Across the nation and overseas, relatives and friends of the nine American hostages held in Lebanon prayed for their safe and spedy return.

A message addressed to the captors of Terry Anderson, the longest-held American hostage, and Thomas Sutherland, a U.S. academician, said: "We, their colleagues and friends, ask you once again in the name of humanity to set them and the others you are holding free."

The message was published in Saturday's edition of Beirut's leading An Nahar newspaper and signed by the Journalists Committee to Free Terry Anderson.

"At this special time of the year, we ask that you consider Sheikh Fadlallah's words, and please relay to Terry, Tom and the others that they are not forgotten . . . we pray for them every day," it said.

In Seattle, members of the Moscow Circus were to receive 130 handmade Christmas stockings, stuffed with donated gifts ranging from apples from the Washington State Apple Commission to Christmas cards made by second grade students at a nearby school. The circus is on a five-day run in Seattle, and a Christmas party was being thrown by the staff of the downtown hotel where they are staying.

But some other Soviets might be disappointed.

Gloria and Edwin Firmage of Salt Lake City had invited members of the Soviet arms control inspection team to their home for Christmas dinner as a peace gesture. Federal officials, however, vetoed the idea, citing logistical and security problems.

Instead, the couple will host a party at the clubhouse of the apartment complex in which the Soviet inspection team is staying.

Like the Grinch who stole Christmas, Laguna Beach, Calif., police officers took the holiday away from an Anaheim family - only to become Santas and give it back again.

Acting on a tip, police Thursday seized allegedly stolen property from the apartment of Charmaine Warden and her children, leaving only a mattress and dining-room set. But Friday, feeling a change of heart, the officers collected $120 at the police station and enlisted the help of their wives and delivered Christmas goodies to the home.

"We felt bad for the kids," Sgt. Ray Lardie said. "You know, Christmas is for the kids, and we took it from them."