In a medium skillet, heat 1 tablespoon sesame oil over medium-high heat. Saute mushrooms and sweet pepper in oil until just tender. Add garlic and saute 1 additional minute. Remove from heat and set aside.
In a small bowl, whisk remaining sesame oil, soy sauce, rice vinegar, ginger, and sesame seeds until smooth. Return veggie pan to medium heat and add sauce. Bring to a low simmer.
Add lo mein noodles and scallions to sauce and toss into sauce until coated. Cook over medium heat until noodles are heated through. Season noodles with salt and pepper to taste. Serve hot and enjoy!