In a glass baking dish, add soup, milk, crackers & pepper. Mix well. Add green beans to mixture. Mix well & spread out evenly in dish.
Bake uncovered 25 minutes.
Top with onions. Bake another 5-10 minutes, or until top is golden brown.
Preparing in advance? Make the casserole as stated but instead of placing it into the oven, cover it with either plastic wrap or foil and put it in the refrigerator. For best flavor, bake within one to two days.