Prepare the Sauce
In a small bowl, mix soy sauce, oyster sauce, hoisin sauce (if using), and cornstarch with ½ cup water. Set aside.
Cook the Beef
Heat 1 tablespoon oil in a large wok or skillet over medium-high heat.
Add beef slices in batches, searing 2–3 minutes until just browned (don’t overcrowd). Remove and set aside.
Cook the Vegetables
Add remaining oil to the pan.
Sauté garlic, ginger, and onion for 1 minute until fragrant.
Add broccoli, carrots, bell peppers, and snap peas. Stir-fry for 4–5 minutes until crisp-tender.
Combine & Thicken
Return beef to the pan. Pour in the sauce.
Stir everything together and cook for another 2–3 minutes until the sauce thickens and coats the beef and veggies.
Finish & Serve
Garnish with sesame seeds and green onions if desired.
Serve hot over steamed rice or noodles.