Thanksgiving dinner is going to cost a lot this year, and short of something as drastic as ignoring it, there may be amore satisfactory way to cut back on costs. But you will have to be willing to strike out in new directions - such as your backyard.

Even if the barbecue grill is already gathering dust in the garage rafters, get it down and cook on it.

An eat-in Thanksgiving cook-out has more going for it than the fact that the work is being shared. The flavor of foods cooked on a grill is so good that little needs to be added to them and you can cut back on the frills. At the same time you can remind your family that simpler food is healthier. And you can plan more carefully so that there are fewer leftovers. With the exception of cold turkey, most meal remains tend to just sit in an obscure corner of the refrigerator.

In addition, simpler dishes are easier of this kind of cookout is the fact that the food needs very little tending, other than an occasional look to see that the coals are hot enough and a check of the side dishes to see if they are ready. Which means that even if it snows on Thanksgiving, no one has to stand out in it watching the food cook.

But even with a cook-out dinner you will still have to budget more money for the meal than you did last year.

Take the turkey.A 10-pounder, which is about as small as you can get, will cost you at least $1.60 more this year than last. A larger one will set you back considerably more.

When you go to stuff the turkey, one simple and essential ingredient, celery, will cost you 10 to 20 cents more per bunch. The cranberries, without which there is no Thanksgiving for many people, are 10 to 15 cents per pound more.

Greens for an ordinary salad will cost you 20 cents more per pound. And if you were thinking of being extravagant and stuffing the turkey with an oyster dressing, you'll have to fork over another 40 cents for a 12-ounce container, now approximately $2.50.

But there are a few bright spots.

Yams were 4 pounds for $1 in 1977, this year that $1 will you 5 pounds. Yellow onions can be purchased for 12 cents a pound, 7 cents less than last year's price. Cans of pumpkins are still going for 50 cents each and canned cranberry sauce is still priced at three cans for $1. You can buy five cucumbers for $1 instead of four for 89 cents.

Since there may be some difficulty selling the family on a Thanksgiving dinner whose centerpiece is a yam pie, even if you mash the yams and shape them like a turkey, and you have thus far not been invited out for dinner, the cook-out approach could be your salvation.

The only hitch comes when you must consider the size of the grill in relationship to the number of people coming for dinner. There are two solutions to the problem of too-small grill versus too-many people.

Invite your neighbors to Thanksgiving dinner if they own a large grill. Then borrow their grill and use it to roast the turkey, using your own for the vegetables. The alternative, unless you are a two-grill family, is cook the turkey on the grill and the vegetables in the oven. They take anywhere from 40 minutes to an hour. During the last 15 minutes of their cooking time, carve the turkey, remove the stuffing and when the vegetables are done, sit down to dinner.

There will be no burnt-on-greasy turkey roasting pan, few side dishes to wash and the foil used to cook the vegetables can be recycled to wrap the leftovers. The food tastes so good this way you can dispense with the marshmallows, cream sauces, fancy stuffing ingredients.

The "indoor" cook can do the preparatory work, and make the stuffing, salad, cranberry relish, pumpkin pie and "nibbles" for before dinner. Everything else is done outside or cooks without tending in the oven.