With or without a crust, quiches are baked in a pie pan from start to finish and all of the filling ingredients are mixed together. Frittata, on the other hand, is prepared in a skillet on the stove and often just finished in the oven. It’s more similar to an omelet, where the veggies and meat are cooked first; then the eggs are poured over the top. It also tends to have a higher ratio of eggs to dairy, if milk or cream is even used at all.