In a large pot or dutch oven pot, over medium-high heat, add the oil and diced onions. Cook until they're softened, while stirring occasionally, for about 5 minutes.
1 tablespoon extra-virgin olive oil, 1 small yellow onion
Add in the ground beef and cook & crumble until the beef is no longer pink. Drain any excess grease/fat from the pot.
1 pound ground beef
Stir in the garlic and packet of taco seasoning in and mix until fragrant and the meat is coated.
3 cloves garlic, 1 packet (1 ounce) taco seasoning
Add the beef broth, beans, tomato sauce, diced tomatoes, diced green chilies, and corn. Stir well.
2 cups beef broth, 1 can (15 oz) pinto beans, 1 can (15 oz) black beans, 1 can (15 oz) tomato sauce, 1 can (14.5 oz) petite diced tomatoes, 1 can (4 oz) diced green chilies, 1½ cups frozen corn
Bring the soup to a boil, then reduce heat to medium low, and let the taco soup simmer (uncovered) for 20-30 minutes.
Serve immediately with your favorite taco soup toppings like sour cream, avocado slices, shredded cheese, tortilla strips, and chopped cilantro.