Preheat your oven to 350°F (175°C) and lightly spray a 9x13-inch baking dish with nonstick cooking spray.

Cook the bacon in a skillet over medium-low heat until crispy, about 10–12 minutes. Remove and crumble once cooled.

Sauté diced yellow onions in the same skillet until translucent, about 5 minutes.

Add sliced button mushrooms and cook until browned and tender, then add minced garlic and stir for an additional minute.

In a mixing bowl, combine the sautéed mixture with cream of mushroom soup, crumbled bacon, milk, and cheese. Season with salt and pepper.

Gently fold in the drained green beans into the mixture.

Pour the mixture into the prepared baking dish and top with French fried onions. Bake uncovered for about 30 minutes.