Method:
Preheat the oven to 425°F.
Toss onions, bell peppers, oil, salt and pepper together on a large baking sheet. Roast until just tender, about 10 minutes. Add asparagus, toss well and roast until vegetables are golden brown and tender, 15 to 20 minutes more. Add turkey, toss well and set aside.
Mix eggs, egg whites, flour, baking powder, milk, salt and pepper together in a medium bowl. Arrange vegetable mixture in pie crust, then pour egg mixture over the top. Scatter cheese over egg mixture and bake until golden brown and cooked through, about 45 minutes. (Tent with foil if top gets too dark before quiche is cooked through). Set aside to cool for 10 minutes before slicing and serving.