Heat oil in medium nonstick skillet over medium-high heat.
Add onion, bell pepper, and jalapeños (if desired); cook, stirring frequently, for 4 to 5 minutes, or until onion is translucent. Reduce heat to medium-low.
Add eggs and egg whites; cook, stirring frequently, for 4 to 5 minutes, or until eggs are set. Remove from heat.
Top each tortilla evenly with egg mixture and cheese.
Fold each tortilla in half; cook in medium nonstick skillet over medium-high heat, for 4 to 5 minutes, turning once, until cheese is melted and tortilla is golden brown.
Tip: You can cook quesadillas you are going to eat or serve, and you can tightly wrap the others and refrigerate for 3 to 4 days (or freeze them). This is a great way to have breakfasts prepared in advance.