Preheat oven to 350 degrees F (175 degrees C). Grease a 3-quart casserole dish with cooking spray.
Combine 3/4 cup white sugar and cinnamon in a large bowl.
Cut each biscuit into 4 pieces and toss in sugar mixture until well-coated. Transfer to prepared casserole dish.
Heat 1/2 cup plus 2 tablespoons margarine in a saucepan over medium heat until melted, 3 to 5 minutes. Stir in remaining 1/2 cup white sugar, peanuts, and brown sugar. Pour over biscuits in the casserole dish, trying to moisten them evenly.
Bake in the preheated oven until golden, about 40 minutes. Remove from oven, gently mix, and return to oven until puffed and browned, about 15 minutes more.
Cool casserole slightly before serving, about 15 minutes.