1. Heat oven to 350°F.
2. Stir together sour cream, 1/2 cup brown sugar, eggs, 2 tablespoons flour, vanilla, lemon juice and salt in large bowl with whisk. Add apples; stir until well blended. Spoon into unbaked crust.
3. Stir together oats, remaining 3/4 cup flour, remaining 1/4 cup sugar and cinnamon. Place peanut butter and butter in small microwave-safe bowl. Microwave at MEDIUM (50%) 30 seconds or until butter is melted. Stir mixture until smooth. Add to oat mixture; blend until crumbs are formed. Sprinkle crumb mixture evenly over apples.
4. Bake 55 to 60 minutes or until apples are tender and topping is golden brown. Cool completely on wire rack. Cover; refrigerate leftover pie. Makes 8 servings.