Toss the sliced beef with baking soda in a bowl and let rest for 20 minutes to tenderize.
Rinse the beef thoroughly under cold water to remove the baking soda, pat dry, and toss with cornstarch, salt, and pepper.
Whisk together the light soy sauce, dark soy sauce, oyster sauce, sugar, and sesame oil in a small bowl to create the sauce.
Cook the lo mein noodles in boiling water according to package instructions until al dente, then drain and rinse with cold water.
Heat 2 tablespoons of oil in a wok or large skillet over high heat until smoking.
Add the beef in a single layer and sear for 2 minutes until browned, then remove from the pan and set aside.
Add the remaining oil to the pan and stir-fry the garlic and the white parts of the scallions for 30 seconds.
Add the carrot, red bell pepper, and snow peas; stir-fry for 2-3 minutes until crisp-tender.
Add the noodles and the sauce to the pan, tossing vigorously over high heat for 1-2 minutes until evenly coated.
Return the beef to the pan, add the green scallion tops, toss once more to heat through, and serve immediately.