1Preheat the oven to 350 degrees F (175 degrees C).
2Place the broccoli into a large saucepan and fill with about 1 inch of water. Bring to a boil, and cook just until tender, about 3 minutes. Drain and transfer to a 4 quart casserole dish.
3In a separate pan, combine the processed cheese and margarine. Cook over medium heat, stirring constantly, until cheese has melted. Remove from the heat and stir in the sour cream. Pour evenly over the broccoli in the casserole. Stir together the crackers and margarine; spread over the top of everything.
4Bake in the preheated oven until the top is browned, about 25 minutes.