Heat oven to 400°F. Unroll pie crust in ungreased 13x9-inch pan. Press crust in bottom and 1/4 inch up sides of pan, cutting to fit; press seams firmly to seal. DO NOT PRICK CRUST. Bake 10 minutes. Remove from oven; immediately press bubbles down with back of wooden spoon.
Reduce oven temperature to 350°F. In large bowl, beat all filling ingredients with wire whisk until blended. Pour over partially baked crust.
Bake 40 minutes. Meanwhile, in medium bowl, mix brown sugar, oats, flour and cinnamon. Cut in butter, using pastry blender (or pulling 2 table knives through ingredients in opposite directions), until mixture looks like coarse crumbs.
Sprinkle streusel over filling. Bake 15 to 20 minutes longer or until knife inserted in center comes out clean (surface may be puffy in spots). Cool completely on cooling rack. Refrigerate at least 2 hours before serving.
In chilled medium deep bowl, beat whipping cream and powdered sugar with electric mixer on high speed until soft peaks form. Cut dessert into squares; serve with whipped cream. Cover and refrigerate any remaining dessert.