You can use reds, yukons or brown potatoes for this. clean potatoes, do not peel, then chop into medium cubes, Chop whole onion.
Put potatoes, onion, garlic, salt and pepper in baking dish and mix well. Then add soup mix and olive oil. You want enough olive oil to not just coat but to have extra to keep everything moist. Mix all together and well.
Bake at 350 for 45 minutes to an hour or until potatoes are tender.