Heat the olive oil in a large skillet over medium heat.
Add diced onion and cook for 3–4 minutes until softened.
Stir in the bell peppers and cook for another 3–4 minutes.
Add the garlic and cook until fragrant, about 30 seconds.
Push the veggies to the side and add the ground beef. Cook until browned, breaking it up with a spoon.
Drain any excess grease if needed.
Add the diced tomatoes, cooked rice, Italian seasoning, salt, and pepper.
Stir to combine everything well and simmer for 5–7 minutes.
Top with shredded cheddar cheese and let it melt, covered, for a couple of minutes.
Sprinkle with parsley if using, then serve hot.