Preheat oven to 450 degrees. Arrange chicken in a 9×13, foil-lined baking dish. Drizzle chicken with olive oil and season with ¼ teaspoon salt and ¼ teaspoon pepper. Roast for 45 minutes. Slice chicken.
Reduce oven to 350 degrees.
Bring a large pot of water to boil. Add cauliflower and cook for 6 minutes. Strain cauliflower.
In a 9x13 baking dish, stir together cauliflower, chicken, 1 cup monterey jack cheese, cheddar cheese, bacon pieces, green onions, garlic powder, ½ teaspoon salt, and ¾ teaspoon pepper. Top with remaining 1 cup of monterey jack cheese.
Bake for 25 minutes.
Recipe by Rachel Schultz at https://rachelschultz.com/2013/05/01/loaded-cauliflower-chicken-casserole/