Preheat your oven to 450°F. Prepare a 9"x13" baking dish by spraying it with nonstick cooking spray.
Cut the baby gold potatoes into 1-inch cubes.
In a large mixing bowl, combine the potato cubes with salt, pepper, and ¼ cup of the ranch dressing. Toss to coat evenly.
Spread the seasoned potatoes evenly in the prepared baking dish. Reserve the mixing bowl for later use with the chicken.
Bake the potatoes in the oven for 30 minutes, stirring every 10 minutes, until they are almost cooked through but not yet fork-tender.
While the potatoes are baking, place the chicken cubes into the same mixing bowl. Add salt, pepper, and the remaining ¼ cup of ranch dressing, mixing well to coat the chicken evenly.
After 30 minutes, remove the baking dish from the oven and reduce the oven temperature to 400°F.
Arrange the marinated chicken pieces evenly over the partially cooked potatoes. Cover the baking dish with aluminum foil (remember to use oven mitts, as the dish will be very hot).
Return the dish to the oven and bake for an additional 20 minutes, or until the chicken is fully cooked and reaches an internal temperature of 165°F.
Remove the foil, then top the casserole with shredded Mexican cheese blend, crumbled bacon, and diced green onions.
Place the dish back in the oven for another 8-10 minutes, or until the cheese has melted and is bubbly.