Butter or grease 8 X 8 X 2 baking dish or a 10" pie plate.
Combine brown sugar, flour, both sugars, oats and cinnamon in a large bowl.
Cut in butter 'til there are only small pea-size pieces.
Place apples in a large bowl.
Toss apples with 1/2 of butter/crumb mixture (about 1 3/4 cups).
Place coated apples in prepared pan.
Separately, mix orange juice and vanilla together.
Pour over apples.
Add chopped pecans to remaining crumb mixture and sprinkle over apples in pan.
Bake at 325° 'til juices are bubbly and topping is dry, about 40 minutes.
Serve warm with ice cream.