Preheat oven to 425°F. Spray a 9×13-inch baking dish with nonstick cooking spray and set aside.
Heat a large skillet over medium heat, then add olive oil and the chopped onion. Sauté the onion about 4 minutes until softened.
Add the ground beef. Cook until browned (about 8 minutes). Drain any grease.
Add the chopped mushrooms and cook until softened, about 5 minutes.
Add the garlic, bell pepper, salt, pepper, and ranch seasoning. Stir well.
Add the ground beef mixture to the prepared baking dish.Spread the uncooked rice evenly over the meat mixture.
Pour the French onion soup evenly over the rice.
Pour the beef broth over the top.
Add the butter pats on top.
Cover tightly with aluminum foil and bake for 40 minutes.
After 40 minutes, remove the foil and continue baking, uncovered, for 20 more minutes, or until the rice is cooked and is tender.
Fluff the rice with a fork, garnish as desired, and serve.