Preheat oven to 350 degrees F. Lightly coat a 3 quart casserole dish with non stick spray and set aside.
Place the green beans in a pot of lightly salted boiling water and cook until fork tender (about 10 minutes). Drain and set aside.
Meanwhile, whisk together the cream of mushroom soup, milk, Worcestershire sauce and pepper directly in the casserole dish, until smooth.
Add the green beans, 2/3 cups of the onion strings and all of the cheddar cheese. Stir to coat the green beans.
Place in the oven for 25 to 30 minutes, until the center is bubbly. Remove from the oven and sprinkle with the remaining fried onion strings. Place back in the oven for an additional 5 minutes. Enjoy right away.