Cook ramen noodles according to package instructions. Drain and set aside.
In a large skillet or wok, heat oil over medium-high heat.
Add sliced chicken and cook until browned and cooked through, about 5-6 minutes.
Add garlic and ginger, cooking for another minute until fragrant.
Toss in broccoli, carrots, and bell pepper. Stir-fry for 3-4 minutes until tender-crisp.
In a small bowl, whisk together soy sauce, oyster sauce, brown sugar, and sesame oil.
Add cooked noodles and sauce to the skillet. Toss everything together until well combined and heated through.
Garnish with green onions and sesame seeds before serving.