Preheat oven to 375°F.
Fill hashbrowns carton to fill line with hottest tap water. Let stand 12 minutes. Drain any excess water.
Meanwhile, cook bacon and onion over medium-low heat in an ovenproof 9 to 10-inch wide nonstick skillet. Stir only a few times until onions soften and lightly brown, and bacon crisps, 12-15 minutes. Remove with a slotted spoon.
Add enough oil to drippings in pan to make about 2 tablespoons. Spread potatoes evenly in pan and slightly up sides, and gently press down.
Cook on medium-high heat until edges begin to brown, about 5 minutes. Remove from heat.
Arrange cheeses and bacon over potatoes.
Whisk eggs, milk, cream and pepper until blended. Pour evenly into pan. If pan handle is plastic, wrap in a double layer of aluminum foil to protect in oven. (Alternatively, potatoes can be slipped into a 9-inch glass pie dish before adding cheese and egg
Bake 25 minutes until puffed and set in center. Serve in wedges.