01 - Toss the sliced beef with 1 tbsp soy sauce and 1 tsp cornstarch in a bowl. Let sit for 10 minutes to tenderize.
02 - Cook the lo mein noodles according to package directions. Drain thoroughly and set aside.
03 - Whisk together 3 tbsp soy sauce, oyster sauce, hoisin sauce, sesame oil, sugar, 2 tbsp water, and 1 tsp cornstarch until smooth and combined.
04 - Heat 1 tbsp oil in a large wok or skillet over high heat. Add the marinated beef and stir-fry for 2-3 minutes until browned. Remove and set aside.
05 - Add another 1 tbsp oil to the wok if needed. Stir-fry broccoli and bell pepper for 2 minutes. Add 2 tbsp water, cover, and steam for 1-2 minutes until just tender.
06 - Add garlic and green onions to the vegetables. Stir-fry for 30 seconds until fragrant.
07 - Return beef to the pan. Add cooked noodles and pour in the sauce. Toss over high heat for 2-3 minutes until sauce thickens and everything is evenly coated.
08 - Transfer to plates and garnish with toasted sesame seeds and additional green onions if desired.