Step 1: Prepare the BBQ Chicken Filling
Preheat your oven to 375°F (190°C). Lightly grease a 9×13 inch (23x33cm) baking dish. In a large bowl, combine the shredded chicken with 1 cup of the BBQ sauce, olive oil, chili powder, smoked paprika, garlic powder, onion powder, and black pepper. Mix until the chicken is evenly and thoroughly coated.

Step 2: Create the Creamy Ranch Layer
In a separate bowl, using a hand mixer or a sturdy whisk, beat the softened cream cheese, sour cream, and ranch dressing together until completely smooth and lump-free. Stir in the drained diced green chiles.

Step 3: Assemble the First Layer
Spread about ½ cup of the remaining plain BBQ sauce evenly over the bottom of the prepared baking dish. Arrange a layer of tortilla quarters over the sauce, overlapping slightly to cover the bottom completely.

Step 4: Build the First Flavorful Stratum
Spread half of the creamy ranch mixture over the tortilla layer. Top with half of the BBQ chicken mixture. Sprinkle evenly with half of the black beans, half of the corn, half of the diced red bell pepper, and a quarter of the diced red onion. Sprinkle with 1 ½ cups of the Colby Jack cheese and 1 cup of the cheddar cheese.

Step 5: Repeat the Layers
Place another layer of tortilla quarters over the cheese. Repeat the layering sequence: remaining creamy ranch mixture, remaining BBQ chicken, remaining black beans, corn, bell pepper, and another quarter of the red onion. Sprinkle with another 1 ½ cups of Colby Jack and 1 cup of cheddar cheese.

Step 6: Apply the Final Tortilla Layer and Sauce
Top with a final layer of tortilla quarters. Drizzle the remaining ½ cup of BBQ sauce evenly over the top. This will soak into the top tortillas and create a flavorful glaze.

Step 7: Create the Crispy Tortilla Chip Topping
In a medium bowl, combine the crushed tortilla chips, melted butter, and taco seasoning. Toss until the chips are evenly coated. Sprinkle this mixture evenly over the sauced tortilla layer. Finish by sprinkling the remaining ½ cup of each cheese (Colby Jack and cheddar) over the chips. Top with the sliced green onions.

Step 8: Bake, Rest, and Load Up with Freshness
Cover the dish with aluminum foil and bake for 25 minutes. Then, remove the foil and bake for an additional 15-20 minutes, or until the casserole is heated through, the cheese is completely melted and bubbly, and the tortilla chip topping is golden. Remove from the oven and let it rest for 10-15 minutes to set. Serve directly from the dish, allowing everyone to top their portion from the fresh garnish bar: diced tomatoes, avocado, cilantro, olives, a drizzle of crema, pickled jalapeños, and a squeeze of fresh lime juice.