Combine flour, oats, sugar, baking soda and salt in a large bowl. Stir in melted butter and mix until crumbly. Press half of the mixture into a greased 13×9-inch baking dish. Bake 8 minutes.
Combine cranberries, sugar, lemon juice and vanilla in a large sauce pan; cover and cook over medium-high heat until berries pop. Reduce heat to medium and cook until mixture thickens to a jam-like consistency.
Spoon the filling evenly over the crust; sprinkle with reserved crumb mixture. Bake 25 minutes or until the filling is bubbly and the topping is golden brown. Let cool 20 minutes, or until the filling is set. Cut into bars and serve.