Preheat oven to 350°F. In a large bowl, whisk together soup, milk, garlic salt and black pepper. Stir in frozen potatoes, green beans, 1 1/3 cup onions and 1 cup cheese.
Pour mixture into a 13x9-inch baking dish. Bake, uncovered, 30 minutes or until hot and bubbly. Sprinkle with remaining 1 cup cheese and 1 1/3 cups onions.
Bake 5 minutes or until cheese is melted and onions are lightly browned.
Notes
O'Brien potatoes are finely diced potatoes, onions and peppers found in the freezer section of your grocery store near the hash brown potatoes.
Use any cream soup you enjoy, such as cream of chicken or cream of potato.
To make this side dish a meal, add 1 pound cooked ground beef or ground turkey in Step 1.