Oven Preparation: Begin by preheating the oven to 375 degrees Fahrenheit. This step is crucial for ensuring the oven reaches the correct temperature for baking the quiche.
Combine Liquid Ingredients: In a large mixing bowl, thoroughly whisk together the eggs, heavy cream, salt, and black pepper until the mixture is homogenous and smooth. This mixture will form the custard base of the quiche.
Incorporate Cheeses and Onions: Add the shredded cheddar, mozzarella, and Swiss cheeses along with the diced yellow onion and chopped green onions to the egg mixture. Stir these ingredients until they are evenly distributed throughout the mixture. This ensures that each slice of quiche will have a balanced flavor profile.
Prepare the Pie Crust: Unroll the pre-made pie crust and gently press it into a 9-inch pie dish. Make sure the crust is evenly laid out at the bottom and sides of the dish. Optionally, crimp the edges of the crust with a fork to enhance the presentation.
Assemble the Quiche: Pour the cheese and egg mixture into the prepared pie crust, smoothing out the top to ensure an even layer.
Bake the Quiche: Place the pie dish in the preheated oven and bake for approximately 38-40 minutes, or until the quiche is set in the middle and the crust is golden brown. The exact baking time may vary based on the oven, so it is advisable to check the quiche near the end of the baking period.
Cool and Serve: Allow the quiche to cool in the pie dish for 8-10 minutes after removing it from the oven. This resting period helps the quiche firm up, making it easier to slice. Serve the quiche warm or at room temperature, as preferred.