1. Pour boiling water over oats in medium bowl; let stand 15 minutes. Heat oven to 350°F. Grease and flour 13x9x2-inch baking pan.
2. Beat butter, granulated sugar, brown sugar and eggs in large bowl until fluffy; stir in oat mixture. Stir together flour, cocoa, baking powder, baking soda and cinnamon; add to butter mixture, mixing well. Stir in apple and nuts. Pour batter into prepared pan.
3. Bake 30 to 35 minutes or until wooden pick inserted in center comes out clean. Cool in pan on wire rack. Drizzle VANILLA GLAZE over top in decorative design. Makes 12 servings.
Combine 1 cup powdered sugar, 1 tablespoon softened butter or margarine, 1 to 2 tablespoons hot water and 1/2 teaspoon vanilla extract in small bowl; beat with spoon or whisk until smooth and of desired consistency.