Slow Cooker Chicken Enchilada Soup

Ingredients

• 2 tablespoons olive oil
• 1 large yellow onion, diced
• 1 small green or red bell pepper, diced
• 3 cloves garlic, minced
• Coarse salt, black pepper to taste
• 4 cups chicken broth
• 1 (10-ounce) can diced tomatoes with green chilies (like Rotel)
• 1 (15-ounce) can black beans, drained and rinsed
• 1 tablespoon chili powder
• 1 teaspoon cumin
• 1/2 teaspoon oregano
• 1 1/4 pounds chicken breasts
• 1 1/2 cups shredded sharp cheddar cheese
• 1 cup sour cream
• 1 avocado, sliced (optional garnish)