In a large pot or Dutch oven, cook the ground beef and onion over medium heat until the beef is browned and the onion is softened. Drain off any excess grease.
Stir in the taco seasoning, kidney beans, pinto beans, black beans, diced tomatoes, Rotel, chopped green chilies, and beef broth.
Bring the soup to a boil, then reduce heat and simmer for at least 15 minutes, or longer for flavors to meld.
Serve hot with your favorite toppings.
Notes
For a slower cooker version, brown the beef and onion on the stovetop, then transfer everything to a slow cooker and cook on low for 4-6 hours or high for 2-3 hours.
This soup freezes well. Let it cool completely before transferring to freezer-safe containers.
Customize your soup with different beans or vegetables like corn or bell peppers.
Consider this a great option if you are looking for meal planning solutions.