This is a great recipe I got from a friend who got it from www.allrecipes.com. Anyway, it's always a huge hit. It is not low-fat by any means!

Four Cheese Macaroni
Recipe By :allrecipes.com
Serving Size : 6 Preparation Time :0:00
Categories : Casseroles Pasta/Pizza
Side Dishes Vegetarian

Amount Measure Ingredient -- Preparation Method
-------- ------------ --------------------------------
1 tablespoon vegetable oil
16 ounces elbow macaroni
9 tablespoons reduced-calorie margarine
1/2 cup Monterey jack cheese -- shredded
1/2 cup Muenster cheese -- shredded
1/2 cup cheddar cheese, lowfat -- shredded
1/2 cup sharp cheddar cheese -- shredded
1 1/2 cups half and half
8 ounces processed American cheese -- cubed
2 eggs -- beaten
1/4 teaspoon salt
1/8 teaspoon ground black pepper

Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain well and return to cooking pot.
In a small saucepan over medium heat, melt 8 tablespoons butter; stir into the macaroni.
In a large bowl, combine the Muenster cheese, mild and sharp Cheddar cheeses, and Monterey Jack cheese; mix well.
Preheat oven to 350 degrees F (175 degrees C).
Add the half and half, 1 1/2 cups of cheese mixture, cubed processed cheese food, and eggs to macaroni; mix together and season with salt and pepper. Transfer to a lightly greased deep 2 1/2 quart casserole dish. Sprinkle with the remaining 1/2 cup of cheese mixture and 1 tablespoon of butter.
Bake in preheated oven for 35 minutes or until hot and bubbling around the edges; serve.

I usually make it up the day before and bake it around the time I want to serve it. Make sure you cook the noodles al dente (or even a little under since they're going to bake).
Enjoy!