Once the outside edge of the frittata turns lighter in color (about 30 seconds to 1 minute), carefully transfer the frittata to the oven. Bake for 7 to 14 minutes (keep an eye on it), until the eggs are puffed and appear cooked, and the center of the frittata jiggles just a bit when you give it a gentle shimmy. Remove the frittata from the oven and place it on a cooling rack to cool. Garnish with herbs, slice with a sharp knife, and serve.
Baked casserole option: Let the cooked vegetables cool for a few minutes. In the meantime, grease a 9 by 13-inch pan with butter, which works better than cooking spray. Stir the lightly cooled veggies into the egg mixture, then pour it all into the pan. If you reserved any cheese, sprinkle it on top of the frittata now.
Bake for 20 to 25 minutes (keep an eye on it), until the eggs are puffed and appear cooked, and the center of the frittata jiggles just a bit when you give it a gentle shimmy. Remove the frittata from the oven and place it on a cooling rack to cool. Garnish with herbs, slice with a sharp knife, and serve.
