1Heat oven to 375°F. Spray large round pizza pan with cooking spray.
2Measure out 1/3 cup of the oatmeal cookie mix, and set aside.
3In medium bowl, beat remaining cookie mix with the butter, egg and water 2 to 3 minutes or until smooth and creamy. Drop dough onto pan, and spread so it completely covers the bottom.
4Bake 5 to 6 minutes or until edges just begin to turn brown.
5In medium bowl, mix reserved cookie mix, the oats and nuts. Use pastry blender to cut butter into dry ingredients until it is the size of small peas.
In large bowl, toss sliced apples, lemon juice, granulated sugar and cinnamon. Scatter apples on top of partially baked cookie crust, and sprinkle with oat mixture.
7Bake 10 to 12 minutes or until topping is crisp. Cool completely.
8Mix Icing ingredients. Drizzle on top of cooled cookie pizza. Let stand 15 minutes before serving.