Heat oil in large skillet over medium-high heat. Add diced onion and cook for a few minutes until transluscent.
Add ground beef and cook until browned, breaking up meat into smaller pieces as you go.
Reduce heat to a medium-low and tip pan to one side to allow grease to gather and dab with a paper towel to remove most of the grease.
Add taco seasoning and water. Stir and simmer for about 3 minutes.
Add 1/2 cup of the Catalina dressing and stir to combine. Turn heat off.
In a large salad bowl, add lettuce, cheese, the remainder of the Catalina dressing, meat mixture, black beans, and doritos. Toss to combine.
Serve in individual bowls and garnish with tomatoes, green or red onion, avocado, sour cream cilantro, black olives or any desired toppings.
Eat at room temperature or chilled.