Add the cream of mushroom soup, milk and pepper to the slow cooker. Stir until smooth.
Add the green beans, half the French fried onions and half of the cheese. Stir.
Sprinkle over remaining cheese.
Cover and cook on HIGH for 2.5 hours.
You have 3 options for the remaining French fried onions. You can add them without crisping to the top of the casserole. Or place the crock pot insert with the French fried onions on top of the green beans in a 350° degree oven for about 10 minutes until crisp. Or put the French fried onions in a skillet and toast them until golden brown (this is what I did), then sprinkle them over the casserole.
Serve and enjoy.
You can set the slow cooker to warm for your holiday gathering.