Heat the oven to 450°F. Coat a 9 x 13-inch baking dish with nonstick cooking spray.
Cut the baby gold potatoes into 1-inch cubes.
Place the diced potatoes in a large bowl. Season with salt and pepper, then add ¼ cup of the ranch dressing and mix until the potatoes are evenly coated.
Transfer the potatoes to the prepared baking dish and arrange them in an even layer. Keep the mixing bowl nearby; you’ll use it again for the chicken.
Bake the potatoes for 30 minutes, stirring them every 10 minutes. At this stage, they should be nearly cooked but not yet completely fork-tender.
While the potatoes bake, place the cubed chicken in the same bowl used for the potatoes. Season the chicken with salt and pepper and toss it with the remaining ¼ cup ranch dressing.
After the potatoes have baked for 30 minutes, remove the dish from the oven. Reduce the oven temperature to 400°F.
Spread the raw, ranch-coated chicken evenly over the potatoes. Carefully cover the baking dish with aluminum foil. The dish will be extremely hot, so use oven mitts when handling it.
Return the covered casserole to the oven and bake for another 20 minutes, or until the chicken is completely cooked and reaches an internal temperature of 165°F.
Remove the casserole from the oven. Sprinkle the Mexican Cheese blend, cooked and crumbled turkey bacon, and diced green onion evenly over the top.
Return the uncovered casserole to the oven for 8–10 minutes, until the cheese has melted and is bubbling.