In a large glass measuring cup, whisk together the eggs and milk. Season with salt and black pepper.
Use several small skillets (7 to 10-inch) to cook the omelets, over medium to high heat. Spray each skillet with cooking spray.
Gently pour in the egg mixture into each skillet. You'll want to divide the batter evenly in four batches. (2 eggs for each omelet)
Gently push cooked portions from edges toward the center with a spatula so that uncooked eggs can reach the hot pan surface. Continue cooking, tilting pan and gently moving cooked portions as needed.
When top surface of eggs is thickened and no visible liquid egg remains, place sauteed peppers, onions, sausage, and cheese on one side of the omelet. Fold omelet in half using the spatula. With a quick flip of the wrist, turn pan and carefully slide the omelet onto a plate.
Garnish with a dollop of sour cream, spoonful of salsa, and freshly chopped parsley or cilantro. Serve immediately.