Preheat oven to 375 degrees F.
In a large bowl, whisk together eggs, milk, salt and pepper. Stir in roasted red pepper and feta cheese.
In a large skillet, heat oil over medium high heat. Add onion, salt, pepper and asparagus. Cook until softened, about 5 minutes. Add the onion and asparagus to the egg mixture and stir to combine.
Next, spray a 9x13inch baking pan with non-stick cooking spray. Pour the egg mixture into the pan.
Bake until set and golden, about 30-35 minutes.