Preheat the oven to 450°F.
Lightly coat a 9x13-inch casserole dish with nonstick cooking spray or oil.
Dice the potatoes into 1-inch chunks.
In a large bowl, combine the diced potatoes with ¼ cup of ranch dressing, seasoning generously with salt and pepper.
Evenly spread the seasoned potatoes in the prepared casserole dish.
Roast the potatoes for 30 minutes, stirring once midway through to promote even browning.
While the potatoes roast, coat the chicken pieces with the remaining ¼ cup ranch dressing and allow them to marinate.
Once the potatoes are par-cooked, layer the marinated chicken evenly over the top. Cover the dish with aluminum foil and bake for an additional 20 minutes, or until the chicken is fully cooked through.
Remove the foil and scatter the cooked bacon, shredded cheese, and diced green onions over the surface.
Return the dish to the oven, uncovered, and bake for a final 10 minutes, or until the cheese has melted and is bubbling.