Place potatoes in a large baking dish and toss with olive oil, onions and garlic. Salt and pepper, to taste. Arrange potatoes in a single layer and bake at 425-degrees for 30-40 minutes, or until potatoes are tender. Stir potatoes occasionally to brown on all sides to prevent sticking.
When done cooking, remove potatoes from the oven and transfer to a large bowl. Add bacon, green onions, ranch dressing and salt and pepper to taste and gently toss.
Serve immediately or chill until ready to serve.