In a small mixing bowl, combine cream cheese, sour cream, garlic powder and oregano. Spread this mixture into a 9-inch glass pie pan. Spread pizza sauce evenly over the cream cheese mixture. Arrange the pepperoni pieces, green bell pepper and onion over the sauce.
Bake for 10 minutes.
When the dish is removed from the oven, sprinkle the mozzarella cheese over the dish.
Return the pie pan to the oven and bake until the mozzarella cheese has melted.