If you find yourself tied to the meat-and-potatoes routine, try using your noodle - egg noodles, that is. While adding variety to your menus, noodles will provide you with many budget-stretching, nutritious main dishes. Side dishes and desserts containing noodles can also liven up ordinary meals. Noodle casseroles are well-suited for informal entertaining, too, because they can be made in advance, and they go a long way.

Noodles belong to the pasta family. They are distinguished from macaroni and spaghetti products because they are made from a dough containing eggs. Although noodles are not unique to Italy, the Italians have refined noodle-making to a precise art, giving each variety a different name according to shape, chuch as fettuccine, ravioli, tortellini and canneloni.

The familiar egg noodles that American cooks use most frequently come invarying widths, from broad to extra-thin soup noodles. Most recipes specify the width called for.

Here are some noodle recipes. NOODLE-CHEESE CASSEROLE

(Serves 6)

This dish is similar to Italian-style lasagne, but it is easier to assemble and the cheddar cheese lends a distinctive flavor. 1/2 pound broad noodles 1 pound ground beef Salt and freshly gound pepper to taste 2 cups fresh or canned tomato sauce Pinch of basil and oregano 1 cup cottage cheese 1/2 cup sour cream 1 1/2 cups grated cheddar cheese 1/2 cup minced scallions (including some of the green variety)

Prepare noodles according to package directions, cooking just until slightly soft. Drain, and set aside. In large skillet, brown beef in its own fat. Add salt, pepper, tomato sauce and herbs. Simmer 10 minutes. Combine remaining ingredients in a small bowl.

Preheat oven to 375 degrees. Grease a 2-quart casserole. Place half the noodles in bottom of casserole, and top with half the cheese mixture. Repeat, using reamaining noodles and cheese mixture. Pour meat sauce over all. Bake, covered, 45 minutes, or until sauce is bubbly.

NOTE: Cassarole can be assembled in advance and frozen or refrigerated until ready to bake. If freezing casserole, bake at 400 degrees for 1 1/4 hours. MUSHROOM-NOODLE CASSEROLE

(Serves 6 as main dish, 12 as side dish) 1/2 pound broad noodles 3 tablespoons butter 1 small onion, chopped 1/4 pound mushrooms, sliced 8 ounces cream cheese, softened 1 cup sour cream 1 can (10 3/4 ounces) cream of mushroom soup 1/2 soup can of milk 1/2 teaspoon Worcestershire sauce 1/2 teaspoon salt 1/2 teaspoon garlic salt Dash curry powder Dash hot pepper sauce 1/2 cup unseasoned bread crumbs

Prepare noodles according to package directions. Preheat oven to 350 degrees. Grease a 2-quart casserole. In 2 tablespoons of the butter, saute onion and mushrooms until soft but not brown; set aside. In large bowl, with electric mixer at low speed, combine cream cheese, sour cream, mushroom soup, milk and seasonings.

Drain noodles, and stir into cream cheese mixture; add onion and mushrooms. Pour into prepared casserole dish, and sprinkle bread crumbs on top. Dot with remaining butter. Bake, uncovered, 30 minutes.