Add all the ingredients for the avocado dressing to a high speed or regular blender and purée until smooth. Add a tablespoon of water or milk at a time until the desired consistency is reached. Taste for seasoning and adjust as needed.
Spray a large skillet with cooking spray or add in a little oil. Heat the skillet over medium-high heat and then add in the ground beef and onion. Use a wooden spoon or potato masher to crumble the beef as it browns. Add in the remaining ingredients and stir everything together. Turn the heat down to low and let the taco meat simmer for 5-10 minutes.
To assemble, fill a bowl with romaine lettuce and top with a portion of the taco meat. Top with corn, tomatoes, olives, queso fresco and cilantro. Dollop on some of the avocado dressing and finish with tortilla strips or crushed chips.