1 1/4 cups quick-cooking oats
1/2 cup butter, melted – divided use
3/4 cup firmly packed brown sugar – divided use
2 tablespoons all-purpose flour
3 (8-ounce) packages cream cheese, softened
3/4 cup granulated sugar
2 teaspoons grated orange peel
2 teaspoons vanilla extract – divided use
4 large eggs
1/3 cup light corn syrup
In a mixing bowl, combine uncooked oatmeal, 1/4 cup melted butter, 1/4 cup brown sugar, and flour; press into bottom of a 9-inch springform pan. Bake in a preheated oven at 350°F (175°C) for 15 minutes. Cool. Lower oven temperature to 325°F (160°C).
In another bowl, combine softened cream cheese, sugar, grated orange peel, and 1 teaspoon vanilla. Using an electric mixer, beat at medium speed until well blended. Add eggs, one at a time, mixing well after each addition; pour mixture over the crust.
Return to oven and bake for 1 hour and 5 minutes.
Loosen the cake from the sides, cool to room temperature and then chill.
To make the butterscotch sauce, combine remaining brown sugar, light corn syrup, and remaining 1/4 cup butter in a saucepan; bring to a boil, stirring constantly. Remove from the heat and stir in remaining vanilla. Chill until slightly thickened then spoon over the cheesecake.