Preheat oven to 375 degrees. Coat a 13" x 9" baking dish with non-stick cooking spray.
Scrub potatoes and poke each one several times with a sharp knife. Place potatoes on a baking sheet and bake for 45 minutes or until they are soft in the center when pierced with a knife. Remove from oven and allow to cool until they can be easily handled and then chop potatoes in bite-size pieces and transfer to a large mixing bowl.
In a separate bowl whisk together the sour cream, milk, garlic, seasoning salt, and black pepper. Pour the mixture over the potatoes and add 1/2 the green onions and 1-1/2 cups cheese. Use a large spoon to toss until the potatoes are completely coated with the sour cream mixture. Transfer to the prepared baking dish. Top with remaining cheese and chopped bacon.
Cover dish with foil and bake for 30 minutes. Remove foil and cook for an additional 5 to 10 minutes, until cheese is melted and bubbly. Garnish with remaining green onions and serve.
Make-Ahead Instructions: Follow as directed but once you transfer the mixture to the baking dish, top with cheese and reserve bacon for later. Cover with foil and refrigerate. When ready to bake, remove from refrigerator and allow to sit out for 20 minutes or so to take the chill off, then top with bacon and continue as directed. Baking time may need to be longer if the dish is cold when going in the oven.