Bring a large pot of water to a boil over high heat, and add the lo mein noodles or spaghetti. Cook until al dente, about 4-5 minutes, stirring occasionally. Drain and toss with sesame oil; set aside.

In a small bowl, whisk together soy sauce, oyster sauce, brown sugar, and a splash of water until sugar dissolves. Set aside.

Heat a large wok or skillet over medium-high heat and add vegetable oil. Cook ground beef, breaking it apart, for about 5-7 minutes until browned. Remove beef and leave drippings.

In the same pan, add garlic and ginger, stir-fry for about 30 seconds until fragrant. Move quickly to the next step.

Add sliced bell peppers, julienned carrots, and sliced red onion. Stir-fry for about 3-4 minutes until tender-crisp.

Return cooked ground beef to the pan with noodles and pour the prepared sauce over everything. Toss to combine and heat through for 2-3 minutes.

Serve immediately, garnished with sliced green onions and a drizzle of sesame oil if desired.