Au Gratin Potatoes
["3 Tbsp. margarine", "3 Tbsp. flour", "1 1/2 tsp. salt", "1/4 tsp. pepper", "3 c. milk", "12 medium potatoes", "1/4 c. chopped onions", "2 c. shredded Cheddar cheese"]
["In 2-quart saucepan, over medium heat, melt margarine.", "Stir in flour, salt and pepper until blended.", "Continue cooking 2 minutes, stirring constantly.", "Set aside.", "Peel potatoes and slice thin."]
["margarine", "flour", "salt", "pepper", "milk", "potatoes", "onions", "Cheddar cheese"]