Preheat oven to 350 degrees. Coat a 9 x 9-inch baking pan with cooking spray.
Cook onions and red bell pepper in microwave for 2 minutes, to soften.
In a large bowl, add cooked onions and peppers, tomatoes, cottage cheese, yogurt, ½ cup shredded cheese, milk, eggs, egg whites, ½ teaspoon seasoning salt or salt and pepper. Mix together well.
Pour mixture into baking pan. Spread evenly. Cover the top evenly with frozen hash browns. Make sure to break up the chunks of potato. Spray the top generously with cooking spray. Sprinkle top with ½ teaspoon seasoning salt or salt and a little pepper.
Cover casserole with foil and bake for 30 minutes. Remove foil, sprinkle with ¼ cup shredded cheese and bake an additional 30 minutes. To crisp, the hash browns, place under broiler for 2-3 minutes until golden brown. Be sure to keep an eye on it while broiling to not burn.
Remove from oven and let rest for 10 minutes to set. Cut into 6 slices.
This casserole can be reheated and it freezes great too! It can be easily doubled and made in a 13 x 9-inch baking dish.