Preheat your oven to 350°F. While it heats, lightly grease a 9x13 inch baking dish (or similar size) and set it aside. This ensures the dish is ready to fill as soon as your filling is prepared, keeping the workflow smooth and preventing the tortillas from drying out while you work.
In a medium bowl, whisk together the enchilada sauce and BBQ sauce until well combined. In a separate large bowl, combine the shredded chicken with half of the mixed sauce, onion powder, minced garlic cloves, BBQ seasoning, and half of the cheese (2 oz). Mix gently until the chicken is evenly coated and all seasonings are incorporated. The sauce will keep the chicken moist and flavorful as it bakes.
Spread a thin layer of the remaining sauce from Step 2 on the bottom of your prepared baking dish. Warm the tortillas slightly (in a microwave or over a skillet) to make them pliable—this prevents cracking and makes rolling easier. I find that 30 seconds in the microwave wrapped in a damp towel works perfectly. Working with one tortilla at a time, place about 1/3 cup of the chicken mixture from Step 2 down the center, roll tightly, and place seam-side down in the baking dish. Repeat with all 8 tortillas, arranging them snugly in a single layer.
Pour the remaining sauce over the enchiladas, making sure to coat them evenly. Sprinkle the remaining 2 oz of shredded cheese over the top. Bake uncovered for 45-60 minutes, until the cheese is melted and bubbly and the sauce is gently bubbling around the edges. The enchiladas are done when the filling is heated through and the top is golden in spots.
Remove the baking dish from the oven and let it rest for 5 minutes—this allows the sauce to set slightly and makes plating cleaner. I always drizzle fresh lime juice and scatter cilantro over the top just before serving to brighten the rich BBQ flavors with a fresh, zesty finish.