In a bowl, mix soy sauce, oyster sauce, cornstarch, beef broth, sugar, and black pepper.
Heat 1 tbsp oil in a pan over medium-high heat. Add steak slices and cook until browned. Remove from the pan.
In the same pan, add another tbsp of oil. Stir-fry bell peppers, onion, and garlic for 2-3 minutes.
Return the steak to the pan and pour in the sauce mixture. Cook for another 2 minutes until the sauce thickens.
Serve hot over cooked rice.