Heat oven to 350°F. Spray a 6-cup shallow baking dish with nonstick cooking spray. Set aside.
In a large bowl, stir together mayonnaise, cream cheese, milk, scallions, lemon juice, red-pepper sauce, Worcestershire sauce, garlic salt and 1/4 cup of the Parmesan cheese until smooth.
Gently stir in crabmeat to avoid breaking it up too finely. Spoon mixture evenly into prepared baking dish. Sprinkle the remaining 1/4 cup Parmesan cheese over top of crab mixture. Bake at 350°F for 30 minutes, until lightly browned. Let stand 5 minutes.
Sprinkle chopped parsley over top. Serve warm, with low-carb tortilla chips if desired.