Preheat oven to 350 degrees F. Grease a 13 x 9 inch baking pan.
Combine flour, oats, 3/4 cup brown sugar and butter. Mix until crumbly. Reserve 1 1/2 cups of crumb mixture and set aside. Place remaining crumbs in baking dish and spread out to form a crust. Bake for 15 minutes.
Beat cream cheese until fluffy and gradually mix in condensed milk, lemon juice and vanilla. Pour evenly over crust.
In small bowl, combine remaining sugar, cornstarch and cranberry sauce. Spoon over cream cheese mixture and sprinkle reserved crumbs over the top. Bake for 40 minutes. Cool at room temperature and refrigerate after cutting into bars. Store in the refrigerator.