Prep the oven and dish: Heat oven to 400°F (200°C). Lightly oil a 9x13-inch baking dish so nothing sticks.
Crisp the bacon: In a skillet over medium heat, cook the chopped bacon until crisp, 6–8 minutes.
Transfer to a paper towel–lined plate. Reserve 1 tablespoon bacon fat.
Whisk the ranch sauce: In a bowl, mix Greek yogurt, mayonnaise, ranch seasoning, garlic powder, onion powder, smoked paprika, black pepper, and salt. It should be creamy and spoonable.
Season the chicken: Pat the chicken dry.
Toss with the reserved bacon fat (or 1 tablespoon olive oil) and a pinch of salt and pepper. This helps it brown and stay juicy.
Combine in the dish: Add chicken to the baking dish. If using veggies like broccoli or peppers, scatter them in now.
Spoon the ranch sauce over the top and toss gently to coat everything evenly.
Add cheese and bacon: Sprinkle cheddar and mozzarella over the sauced chicken. Top with the crispy bacon.
Bake: Bake uncovered for 22–28 minutes, until the chicken is cooked through (internal temp 165°F/74°C) and the cheese is melted and bubbly.
Finish and rest: Let the bake rest 5 minutes so the juices settle. Sprinkle with chives or green onions before serving.
Serve: Pair with a green salad, roasted green beans, or a side of quinoa, brown rice, or cauliflower rice.