Preheat oven to 350 degrees. Lightly grease a 13 x 9 baking pan. In large bowl combine flour, oats, 3/4 cup sugar and butter. Mix until crumbly. Reserve 1 1/2 cups crumb mixture for topping. Bake 15 minutes and cool completely. In a large bowl beat cream cheese until fluffy, gradually mix in condensed milk, lemon juice, and vanilla until smooth. Pour evenly over crust. In a small bowl combine remaining sugar, cornstarch and cranberry sauce. Spoon over cream cheese mixture. Sprinkle reserved crumb topping over top. Bake 40 minutes, cool at room temperature and refrigerate before cutting. Store in refrigerator.