Preheat your oven to 375°Fahrenheit, then brush a casserole dish with olive oil.
Combine the thawed diced potatoes, savory ham, cream of chicken soup, sour cream, shredded cheese, chopped green onions, and ranch dressing mix in a large bowl. Season with salt and pepper to taste, then mix until well combined.
Spread the potato mixture evenly on the bottom of the prepared baking dish and top it with the remaining cheese and a sprinkle of bacon.
Bake the casserole for 40-45 minutes or until the potatoes are tender and the mixture is bubbly.