In a Dutch oven, saute onion and carrots in oil for 3 minutes. Add the chili powder, garlic, cumin and oregano; cook 1 minute longer., Stir in broth and lentils. Bring to a boil. Reduce heat; cover and simmer for 20 to 22 minutes or until lentils are tender. Stir in the tomatoes, potatoes, beans, salt and pepper. Return to a boil. Reduce heat; cover and simmer 10-15 minutes longer or until potatoes are tender. If desired, garnish with oregano.