Heat oven to 375°F. Spray 9-inch square baking pan with cooking spray. Break up three-fourths of cookie dough in pan. With floured fingers, press dough evenly in bottom of pan to form crust. Bake 15 to 20 minutes or until golden brown.
Meanwhile, in medium bowl, crumble remaining cookie dough. Add oats, brown sugar, pecans, 1/4 teaspoon of the cinnamon and 1/4 teaspoon of the nutmeg; toss and set aside.
In 3-quart saucepan, mix granulated sugar, cornstarch, remaining 1/4 teaspoon cinnamon and remaining 1/4 teaspoon nutmeg. Stir in peaches and lemon juice until thoroughly coated. Heat to boiling over medium-high heat, stirring constantly. Boil and stir 1 minute.
Spoon peach mixture evenly over partially baked crust. Top with oat mixture. Bake 25 to 30 minutes longer or until topping is golden brown and filling is bubbly. Cool 1 hour before serving. Cut into squares.