Cook the Noodles: Boil the lo mein noodles according to package instructions. Drain and set aside.
Prepare the Sauce: In a small bowl, mix soy sauce, oyster sauce, hoisin sauce, brown sugar, sesame oil, and red pepper flakes. Set aside.
Cook the Beef: Heat vegetable oil in a large skillet or wok over medium-high heat. Add the sliced beef and cook for 2-3 minutes until browned. Remove and set aside.
Stir-Fry the Broccoli: In the same pan, add garlic, ginger, and broccoli. Stir-fry for 2 minutes until slightly tender.
Combine Everything: Add the cooked beef and noodles back to the pan. Pour in the sauce and toss to coat everything evenly.
Serve: Garnish with green onions and sesame seeds. Enjoy hot!