The creamy texture in this frittata comes from using whole milk Greek yogurt, and added veggies give it an extra punch that is sure to keep you full throughout the morning.
Preheat oven to 350. Heat olive oil in cast iron skillet over medium heat, or similar oven safe skillet. Dice onion, mushrooms, bell pepper, and sausage links and add to the pan.
Saute for 5-10 minutes, until mushrooms are soft and onions are translucent.
While the veggies are cooking, crack 12 eggs into a large bowl and add Greek yogurt. Whisk to combine. (It may look weird at the beginning, but just keep going and you'll get a smooth and creamy mixture). Stir in grated cheese, salt and pepper.
Pour the egg mixture into the cast iron and gently stir to distribute the veggies and sausage. Let the mixture cook in the pan (without stirring) for 4-5 minutes to set the eggs.
Transfer the skillet carefully to the oven, and cook for 15-20 minutes. Check after 15 minutes, the frittata should look just set throughout. Let cool and slice into 8 servings.