Preheat your oven to 350 degrees Fahrenheit.
Cut the bell peppers in half lengthwise and remove seeds and membrane. Drizzle with a little olive oil and rub both the inside and outside to coat them. Arrange them upside down in two baking pans or one half sheet pan and pre-bake for about 15 minutes, while you're making the stuffing.
In a large skillet over medium high heat, drizzle two tablespoons of olive oil and saute the garlic and onions for one minute.
Add the ground beef and cook until the beef is browned, breaking it up with a spatula as needed.
Drain off any excess liquid from the beef and stir in the diced tomatoes, rice, spinach, Italian seasoning, salt, and pepper. Stir for a minute or two, or until the spinach is wilted.
Remove the bell peppers from the oven and use tongs to flip them over.
Fill the peppers with the beef mixture and top with a sprinkle of cheese. Place them back in the oven and bake for 20 minutes, or until the peppers are soft.
Top with fresh parsley and serve.