Heat the olive oil in a large stock pot or dutch oven over medium high heat.
Add the ground beef to the pot. Cook the beef until browned, breaking up into smaller pieces with a wooden spoon, and no longer pink; approximately 5-7 minutes.
Using a slotted spoon, transfer the beef to a bowl and keep warm. Pour off all but 2 tablespoons of the fat and return the pot to the heat.
Add the onions and cook for 2-3 minutes or until beginning to soften. Stir in the garlic and cook for 1 minute longer.
Stir in the butter and add the peppers, toss to combine.
Cook the peppers until beginning to soften, approximately 3-4 minutes.
Add the tomatoes, vinegar, brown sugar, rice, Worcestershire sauce and beef stock. Bring the soup to a boil then turn the heat to low.
Add the beef back to the pot and simmer for 20 minutes until rice is tender.
Season with salt and pepper, to taste.
Serve immediately.
Notes
Stuffed pepper Soup is a great make ahead dinner or lunch. Store in an airtight container in the refrigerator for up to 5 days.Freeze in a freezer safe container for up to 2 months.