Cook the rice noodles according to the package instructions. Drain and set aside.
In a small bowl, combine the soy sauce, oyster sauce, fish sauce, and brown sugar. Stir until the sugar dissolves. Set aside.
Add the sliced red bell pepper and broccoli florets. Stir-fry for an additional 2-4 minutes until the vegetables are tender-crisp.
Combine the cooked noodles with the sauce mixture in the skillet. Stir-fry for 2 minutes, tossing everything together until the noodles are thoroughly coated and heated.