Impossibly Easy Pumpkin-Pecan Pie

1 cup canned pumpkin (not pumpkin pie mix)
1/2 cup Original Bisquick® mix
1/2 cup sugar
1 cup evaporated milk (from 12-oz can)
1 tablespoon butter or margarine, softened
1 1/2 teaspoons pumpkin pie spice
1 teaspoon vanilla
2 eggs
1/2 cup chopped pecans
1 1/2 cups frozen (thawed) whipped topping
1/4 teaspoon pumpkin pie spice
8 pecan halves, if desired

Heat oven to 350ºF. Spray 9-inch glass pie plate with cooking spray.
In medium bowl, stir pumpkin, Bisquick mix, sugar, milk, butter, 1 1/2 teaspoons pumpkin pie spice, the vanilla and eggs until blended. Stir in chopped pecans. Pour into pie plate.
Bake 35 to 40 minutes or until knife inserted in center comes out clean. Cool completely, about 1 hour.
Stir whipped topping and 1/4 teaspoon pumpkin pie spice. Garnish pie with topping and pecan halves. Store covered in refrigerator.