In a medium bowl, use an electric mixer to combine the cream cheese and the sour cream until smooth. Stir in the garlic, cheddar cheese, parmesan cheese, broccoli, red pepper, and onion until combined.
Spoon the dip into a 1.5 quart (1.4L) baking dish and bake for 25-30 minutes, or until hot and bubbling. Serve with chips, crackers or veggies.
Refrigerate leftovers, and reheat it at 350F for 20-30 minutes, covered with aluminum foil.