Add 2 tablespoons olive oil to a large skillet. Cook onions and peppers until softened.
Add the minced garlic. Cook for 1 minute. Add the ground beef to the skillet. Break up and cook stirringly occasionally until cooked through.
Transfer to a slow cooker. Add in all the remaining ingredients.
Serve in individual bowls topped with the cheese, green onions or chives, and sour cream.