Healthy Mongolian Beef is a lighter version of the classic recipe, perfect for those who are watching their calorie intake. This recipe uses lean beef, such as sirloin or flank steak, and reduces the amount of sugar and oil used in the sauce. It also incorporates plenty of vegetables, such as bell peppers and broccoli, to add nutrition and color to the dish. This healthier version still delivers all the flavors of the original recipe without the guilt.