Ann and Neville Mackey, a practical nurse and a supermarket cashier, celebrated an extravagant Christmas yesterday, not with presents, but by bringing 48 strangers into their Rockville home for a sit-down turkey dinner.

The celebration took months of careful planning, nights of work and neither one knows exactly how much money, but as Ann Mackey says, "This is my Christmas. If I don't do anything else for the holiday my family will understand."

Though the 35-year-old nurse shrugs off the gesture, Joseph A. Price, the executive secretary of the Montgomery County Commission on Aging, who rounded up the senior citizen guests for the dinner, was shocked when she suggested it.

"We have people who call to invite two or three senior citizens for Christmas dinner, but she was talking about 50 or 100," Price says of the September phone call he got from Mackay. Mackey did manage by squeezing two big round tables into her small living room, setting three picnic tables in the recreation room, and dressing up the kitchen table with a bright red cloth. Chairs were borrowed from a religious club and from a funeral director, who had never met the Mackeys but was persuaded to help.

Retired chef Harold Neeley, a farmily friend, cooked the two 20-pound turkeys the Mackeys delivered to his Arlington home last week. By 7 a.m. yesterday Neeley was ensconced in the Mackey kitchen like a general ready to take command of his troops, who turned out to be the Mackeys' two daughters and a crew of her friends.

By noon, 60 green salads, tiny cups of cranberry sauce and dressing, giant bowls of sage stuffing and pans of other trimmings were laid out on every kitchen counter.

Ann Mackey, who had worked her regular 7-to-7 shift on Friday and stayed up all night worrying about the party, bustled through the house checking every place setting and decoration.

When her guests arrived, the giblet gravy was simmering in the kitchen and carolers were singing on the front lawn.

The senior citizens, who were brought from several communitits by the Montgomery County Division of Elder Affairs, pronounced the dinner "delicious," the decorations "lovely," and the whole affair "a wonderful surprise" right down to the bright red matchbooks that said, "Glad you came, Ann Mackey."

Mackey, certain from the start that her plan would work, had ordered them printed the same day she called Price last September.

Her husband watched her proudly yesterday from the sidelines as she posed for photographs with her guests, saying "I'm very selfish. I want pictures of all my people and myself."

The Mackeys' daughters, 13-year-old Pearline and 12-year-old Tracey, were told "we might not get as many gifts as we did before because of the dinner," Tracey explained as she raced from the kitchen with two plates heaped with turkey. "But it doesn't matter to me because this is as much of a Christmas as getting presents."