Grease a 9 x 13 inch pan with nonstick cooking spray.
In a large bowl, combine eggs, cream, milk, ricotta, salt, pepper, and onion powder. Mix until no lumps of ricotta remain.
Mix in all of the remaining ingredients. Stir until potatoes are thoroughly coated.
Pour into greased pan. Cover with aluminum foil and refrigerate overnight.
In the morning, remove from refrigerator and leave aluminum foil on top. Heat oven to 350 degrees.
Bake with foil on for 50 minutes or until knife inserted in the center comes out clean.
Remove foil. Return to oven for 5-10 minutes until the top is lightly browned.
Remove from oven and allow to cool for 5 minutes uncovered before slicing.