Add ginger, garlic, soy sauce, 2 teaspoons cornstarch, oil, and red pepper to a resealable plastic bag. Place steak in bag, seal, and place in refrigerator for 20 minutes.
Heat a cooking spray coated frying pan over medium-high heat. Sauté mushrooms, onions, and bell peppers for 3 minutes, until soft, yet crunchy. Spoon mixture into a bowl. Sauté bok choy for 2 minutes or until almost wilted. Add to bowl.
Using same pan, spray with cooking spray. Place half of steak mixture in pan and stir-fry 3 minutes. Spoon mixture into a bowl. Recoat pan with cooking spray and stir-fry other half of steak, 3 minutes. Spoon into bowl.
Whisk together broth and 2 teaspoons cornstarch and pour into pan, scraping up any browned bits from the bottom of the pan. Let boil 1 minute, stirring continually. Place steak ad vegetable in pan and mix with sauce.