Preheat: Preheat your oven to 375°F or 190°C.
Saute: In the oven-safe pan, heat the olive oil over medium heat and sauté the diced pepperoncini until they start to soften.
Mix: In a mixing bowl, whisk the eggs, then add the sautéed pepperoncini and half of the grated cheddar cheese. Stir to combine.
Bake: Pour the egg mixture into the pan, sprinkle the remaining cheese on top, and bake in the preheated oven for about 20-25 min or until edges are golden and the center is firm.
Serve: Once out of the oven, let it cool for few minutes before slicing. Serve the Italian Pepperoncini and Cheese Frittata with your favorite sides or as is.