I found this recipe on All Recipes. This is a great site with tons of great recipes. I really like these bars because they are very simple and very flavorful and they make a ton (36 bars)!

Magic Cookie Bars
Ingredients
* 1/2 cup butter or margarine, melted
* 1 1/2 cups graham cracker crumbs
* 1 (14 ounce) can EAGLE BRAND® Sweetened Condensed Milk
* 2 cups semisweet chocolate morsels (next time I’ll use less – too much chocolate & I love chocolate)
* 1 1/3 cups flaked coconut
* 1 cup chopped nuts

DIRECTIONS
1. Heat oven to 350 degrees F (325 degrees for glass dish). Coat 13×9-inch baking pan with no-stick cooking spray.
2. Combine graham cracker crumbs and butter. Press into bottom of prepared pan. Pour sweetened condensed milk evenly over crumb mixture. Layer evenly with chocolate chips, coconut and nuts. Press down firmly with a fork.
3. Bake 25 minutes or until lightly browned. Cool. Cut into bars or diamonds. Store covered at room temperature.

Here are some variations: (I can’t get other chips here so I can’t try it but I may try the M&M’s variation.)
~7-Layer Magic Cookie Bars: Substitute 1 cup (6-ounces) butterscotch flavored chips* for 1 cup semi-sweet chocolate chips and proceed as directed above.

~Peanut butter flavored chips or white chocolate chips may be substituted for butterscotch flavored chips.

~Magic Peanut Cookie Bars: Substitute 2 cups (about 3/4 pound) chocolate-covered peanuts for semi-sweet chocolate chips and chopped nuts.

~Magic Rainbow Cookie Bars: Substitute 2 cups plain candy-coated chocolate candies for semi-sweet chocolate chips.