In a medium bowl, combine the thinly sliced beef, soy sauce, oyster sauce, and cornstarch. Mix well and let marinate for 10 minutes.
Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat.
Add the marinated beef to the skillet and stir-fry for 3-4 minutes until browned and cooked through. Remove the beef from the skillet and set aside.
Add the remaining 1 tablespoon of vegetable oil to the skillet.
Add the minced garlic and ginger and stir-fry for 30 seconds until fragrant.
Add the red bell pepper, green bell pepper, carrot, broccoli florets, and snap peas to the skillet. Stir-fry for 4-5 minutes until the vegetables are tender-crisp.
Return the cooked beef to the skillet with the vegetables.
Pour in the beef broth and stir to combine. Cook for an additional 2 minutes to heat through and allow the sauce to thicken slightly.
Drizzle the sesame oil over the stir fry and toss to coat evenly.
Remove from heat and garnish with sliced green onions and toasted sesame seeds.
Serve hot over steamed rice or your choice of grain.