Preheat the oven to 375°F.
In a large skillet, heat the olive oil over medium heat. Add the diced onion and bell peppers, sautéing until softened, about 5 minutes.
Add the diced ham and cook for an additional 2-3 minutes until heated through. Remove from heat and let cool slightly.
In a large mixing bowl, whisk together the eggs, whole milk, salt, and black pepper until well combined.
Stir in the sautéed vegetable and ham mixture, along with the shredded cheddar cheese.
Pour the egg mixture into the pre-made pie crust, spreading it evenly.
Bake in the preheated oven for 35-40 minutes, or until the quiche is set in the center and lightly golden on top.
Allow the quiche to cool for 10 minutes before slicing and serving.