Step 1: In a bowl, combine sliced steak with soy sauce and cornstarch, then let marinate for 10 minutes.
Step 2: Heat 1 tablespoon oil in a large skillet or wok over high heat, add steak in a single layer, and cook for 2-3 minutes until browned, then remove and set aside.
Step 3: Add remaining oil to the skillet, then sauté onion and bell peppers for 4-5 minutes until slightly softened.
Step 4: Stir in garlic and ginger, cooking for 1 minute until fragrant.
Step 5: Pour in beef broth and oyster sauce, bring to a simmer, then return steak to the skillet.
Step 6: Cook for 2-3 more minutes until sauce thickens and steak is heated through, then stir in black pepper.
Step 7: Garnish with green onions and serve immediately over cooked rice.