Combine 1 tablespoon soy sauce, sesame oil, and cornstarch in a bowl; add beef and marinate for 15 minutes.
Whisk remaining soy sauce, beef broth, and oyster sauce in a small container to create the finishing sauce.
Heat 1 tablespoon vegetable oil in a wok or heavy skillet over high heat until wisps of smoke appear.
Add beef in a single layer; sear for 90 seconds without stirring, then stir-fry for 1 minute until browned and remove from pan.
Add remaining oil to the pan; incorporate broccoli, carrots, and peppers, stir-frying for 3 minutes.
Add snap peas, garlic, and ginger; cook for 45 seconds until aromatic.
Return the beef to the wok and pour in the finishing sauce.
Toss continuously over high heat for 60 seconds until the sauce emulsifies and coats the ingredients.
Serve immediately over rice or noodles.