Cook sausage according to package directions; cut into 1/2-inch pieces and set aside. In a bowl, combine green onions, bell pepper, chilies and cilantro; set aside.
Spray a 5- or 6-quart slow cooker with cooking spray. Layer a third of hash browns, sausage, green onion mixture and cheese. Repeat layers twice.
In large bowl, whisk eggs, milk, salt and pepper; pour over casserole. Cover and cook on low for 7-8 hours or until a thermometer inserted into the center reads 160 degrees.