Preheat oven to 350°F.

Mix flour, oatmeal, brown sugar, margarine, baking soda and salt. Take out 1 1/2 cups and set aside.

Spray 9x13 pan. Pat remaining mixture in pan, raising edges slightly.

Bake 20 minutes at 350°F

Melt 2 tablespoons butter; add 1 cup M&Ms. Smash with spoon; add sweetened condensed milk. Pour over crust

Mix remainig M&Ms and nuts, if desired, into reserved oatmeal mixture.

Sprinkle over filling. Bake an additional 20 minutes. Cool and cut into squares.