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

Cook the bacon in a large skillet over medium-low heat until crispy and golden brown, about 8-10 minutes. Drain on paper towels and crumble when cooled.

Sauté the diced yellow onion in the bacon grease over medium heat until translucent, about 5 minutes.

Stir in the chopped button mushrooms and cook until golden brown, about 5 minutes. Add the minced garlic and sauté for an additional minute.

Pour in the cream of mushroom soup, crumbled bacon, milk, and Monterey Jack cheese into the skillet. Stir over low heat until melted and smooth. Season with salt and pepper.

Fold in the drained canned cut green beans until evenly coated.

Pour the mixture into the prepared baking dish, spreading evenly.

Sprinkle the French fried onions over the top and bake uncovered for about 30 minutes, until hot and bubbly.