Preheat oven to 450 degrees. Cut up red potatoes into uniform chunks. Toss in olive oil, garlic salt and black pepper.
Roast potatoes at 450 for 40-45 minutes, stirring occasionally.
In a large bowl, toss potatoes with vinegar while hot.
Cool completely. Add remaining ingredients and mix well. Top with chopped green onions, if desired. If you like a creamier salad, you may add a little more mayo. I actually like this a little on the tangy side, so I use less mayo.