Preheat oven 400°F. Grease a 9x13-inch casserole dish with nonstick spray.
Heat the oil in a large skillet over medium-high heat. Saute the onion and celery until soft and translucent, 2-3 minutes. Add the cauliflower rice, cooked rice and stir to coat and warm. Transfer to the prepared baking dish.
2 Tablespoons olive oil, 3/4 cup yellow onion, 3 ribs celery, 24 ounces frozen cauliflower rice
Mix in the cooked chicken, salt, garlic powder, ranch dressing, hot sauce, 1 cup of cheddar cheese, and cubed cream cheese and stir to combine. Sprinkle the remaining cup of shredded cheese on top.
1 lb cooked chicken, 1/2 cup ranch dressing, 3/4 cup hot sauce (I used Frank's Red Hot), 2 cups shredded cheddar cheese, 1 teaspoon garlic powder, 1/2 teaspoon kosher salt, 4 ounces block full-fat cream cheese
Bake in the preheated oven for 25-30 minutes, until the casserole is bubbling around the edges and the cheese is melted and golden brown on top. Allow it to cool for 10 minutes to set up slightly before serving. Top with green onions, ranch dressing, or blue cheese.