In a large skillet over medium heat, cook the ground beef for about 8 to 10 minutes, breaking it apart with a spatula as it browns. Sprinkle the taco seasoning mid-way through cooking, and mix it as you cook. Once the meat is fully cooked, drain any excess grease. Or use a slotted spoon to remove it from the pan during assembly.
Assemble:
In a large bowl or on individual plates, make a base with the chopped romaine lettuce. Top with the cooked ground beef, black beans, corn, halved tomatoes, and diced avocado.
Sprinkle the shredded cheese over the top and add a generous handful of tortilla chips for crunch.
Serve:
Add a dollop of sour cream, if using. Drizzle your favorite dressing over the top, and enjoy.