Preheat oven to 325º. Grease bottom of an 8 inch square or 11x7 inch rectangular baking dish.
Whisk together flour and next 5 ingredients. Add butter and orange juice to flour mixture, stirring until moist and crumbly. I recommend doing this in a stand mixer with the paddle, but you can also do it by hand.
Reserve ½ c oat mixture. Press remaining oat mixture into the bottom of an 11 x 7-inch baking dish coated with cooking spray.
To prepare topping, combine cranberries, sour cream, sugar and remaining ingredients in a medium bowl, stirring well. Spread cranberry mixture over prepared crust; sprinkle reserved oat mixture evenly over filling.
Bake at 325º F for 35 to 40 minutes or until edges are golden. Let cool completely in pan on a wire rack.