Cook the Noodles: Bring a large pot of salted water to a boil. Cook the noodles according to package instructions. Drain and set aside, tossing with a bit of sesame oil to prevent sticking.
Marinate the Beef: In a bowl, combine sliced beef with soy sauce, oyster sauce, and a pinch of salt and pepper. Let it marinate for about 10-15 minutes.
Stir-fry the Beef: Heat vegetable oil in a large skillet or wok over medium-high heat. Add the marinated beef and stir-fry for about 3-4 minutes until browned and just cooked through. Remove the beef from the skillet and set aside.
Sauté the Garlic: In the same skillet, add sesame oil and minced garlic. Sauté for about 30 seconds until fragrant, being careful not to burn the garlic.
Add Vegetables: Toss in the sliced red bell pepper and snap peas; stir-fry for about 2-3 minutes until the vegetables are just tender but still crisp.
Combine Everything: Return the beef to the skillet, add the cooked noodles, and drizzle with chili garlic sauce. Toss everything together until the noodles are well coated and heated through.
Garnish and Serve: Remove from heat and top with chopped green onions and fresh cilantro if desired. Serve hot.
Notes
Adjust the chili garlic sauce for desired spice level.