Heat olive oil in a large pot over medium heat.
Add chopped onions and bell pepper; sauté until softened.
Stir in minced garlic and cook for another minute.
Add the ground beef, breaking it up with a spoon, and cook until browned.
Sprinkle in chili powder and cumin, stirring to coat the meat.
Pour in the diced tomatoes and kidney beans.
Season with salt and pepper to taste.
Bring the mixture to a simmer, then reduce heat to low.
Cover and let it cook for 30 minutes, stirring occasionally.
Adjust seasoning as needed before serving.