Place the oven rack in the top ⅓ of your oven, and preheat to 350°F.
Warm a 10” cast iron skillet over medium heat, then sauté the bacon until fully cooked and crispy (8-10 minutes). Move the bacon pieces onto a plate lined with a paper towel, leaving 2 tablespoon of bacon grease in the pan.
Keeping the skillet over medium heat, add the scallions, zucchini, and corn kernels. Sprinkle with salt and pepper, then sauté for 3-5 minutes until the vegetables soften but do not brown.
While the vegetables cook, whisk together eggs, cheese, and milk in a mixing bowl, adding a healthy pinch of salt and a few shakes of black pepper.
Whisk gently until evenly combined, then stir in the chopped bacon.
Once the vegetables are cooked, turn the burner off and evenly spread them around the pan. Pour the egg mixture over the vegetables, gently lifting them to allow the eggs to run underneath them.
Transfer the whole skillet to the oven and bake for 30 minutes until the frittata puffs up and turns a golden color.
Remove the skillet from the oven and allow to cool for 10 minutes – the frittata will deflate.
Sprinkle with diced herbs of choice, slice into pieces, and serve warm.