Place potato in a saucepan; cover with water. Bring to a boil; reduce heat, and simmer 15 minutes or until tender; drain. Cool, dice, and set aside.
Heat a medium nonstick skillet over medium heat. Add onion, bell pepper, and garlic; sauté 8 minutes. Add potato, olives, and oregano; cook 1 minute or until thoroughly heated. Remove from heat; stir in cheese. Set aside.
Combine egg whites, eggs, salt, and pepper in a bowl; stir well with a whisk.
Heat 1/4 teaspoon olive oil in a small nonstick skillet coated with cooking spray over medium-high heat. Add half of egg mixture to skillet. Carefully lift edges of omelet with a spatula; allow uncooked portion to flow underneath cooked portion. Cook 3 minutes; flip omelet. Spoon 1 cup potato mixture onto half of omelet. Carefully loosen with a spatula; fold in half. Cook an additional minute on each side. Slide onto a plate. Repeat procedure with 1/4 teaspoon olive oil, cooking spray, egg mixture, and potato mixture.
Note: Substitute 2 cups egg substitute for 8 egg whites and 4 eggs, if desired.