Spray a 6-quart slow cooker with non-stick cooking spray or line it with a slow cooker liner.

In the base of the slow cooker, whisk together the cream of mushroom soup, garlic powder, salt, and black pepper.

Stir in the thawed green beans, Parmesan cheese, and half of the French fried onions.

Secure the lid onto the slow cooker and cook on high for 2-3 hours or on low for 3-4 hours. The casserole is done when it’s hot and bubbly. If needed, switch to the warm setting until ready to serve.

Just before serving, sprinkle the remaining French fried onions over the top of the casserole and serve warm.