Heat oven to 350°F. Spray 13x9-inch pan with cooking spray. In medium bowl, mix 1 cup Bisquick mix and the brown sugar. Cut in 1/4 cup butter, using pastry blender (or pulling 2 table knives through ingredients in opposite directions), until crumbly. Stir in nuts; set aside.
In large bowl, mix apples, cinnamon and nutmeg; spoon into pan. In medium bowl, stir remaining ingredients until well blended. Pour mixture over apples. Sprinkle with streusel.
Bake 45 to 55 minutes or until knife inserted in center comes out clean and top is golden brown. Cool 30 minutes or until set before cutting into squares. Frost with Glaze below.
Browned Butter Glaze
¼ c butter
2 c powdered sugar
1 t vanilla
1-2 t hot water
Heat butter over low heat until golden brown. Remove from heat. Beat in powdered sugar and vanilla. Stir in water, 1 t at a time until smooth and of desired consistency.