Step 1: Prepare the Marinade

• In a small bowl, whisk together soy sauce, oyster sauce, cornstarch, honey, sesame oil, grated ginger, garlic, and red pepper flakes.
• Transfer half of the marinade to a separate bowl for use as the stir-fry sauce.
• Add the sliced steak to the remaining marinade and toss to coat. Let it marinate for at least 15 minutes while you prepare the vegetables.

Step 2: Slice and Prep Vegetables

• Wash and slice the bell peppers into thin strips. Peel and slice the onion into wedges. Set aside.
• Chop green onions and set them aside for garnish.

Step 3: Cook the Beef

• Heat 1 tablespoon of vegetable oil in a large skillet or wok over high heat.
• Add the marinated beef in a single layer, cooking for 2-3 minutes per side until browned but not fully cooked through.
• Remove the beef from the skillet and set it aside on a plate.

Step 4: Stir-Fry the Vegetables

• Add the remaining tablespoon of vegetable oil to the skillet.
• Toss in the bell peppers and onions, stir-frying for 3-4 minutes until they are tender-crisp.

Step 5: Combine and Cook

• Return the beef to the skillet, along with any juices that have accumulated on the plate.
• Pour the reserved sauce over the beef and vegetables, stirring to coat everything evenly.
• Cook for an additional 2-3 minutes, or until the sauce thickens and the beef is cooked to your desired level of doneness.

Step 6: Garnish and Serve

• Remove the skillet from heat and sprinkle with chopped green onions and sesame seeds.
• Serve hot over steamed rice, noodles, or your favorite side dish.