Heat the grapeseed oil in a large nonstick skillet over medium-high heat. Add the pepperoni and fry, turning as needed, until crisp around the edges, about 1 minute. Transfer to paper towels to drain; pour off the fat and wipe out the skillet.
Melt the butter in the skillet over medium heat. Whisk the eggs and milk in a bowl; add to the skillet and season with 1/2 teaspoon salt, and pepper to taste. Cook, running a rubber spatula around the edges and along the bottom to prevent the eggs from sticking, until almost set, 2 to 3 minutes; sprinkle with the cheese, pepperoni and scallion, then cover and remove from the heat to finish cooking, about 1 more minute.