In a mixing bowl, combine the soy sauce, oyster sauce, cornstarch, and water. Whisk until smooth. Set aside.
Heat the vegetable oil in a skillet or wok over medium-high heat.
Add the thinly sliced beef to the skillet. Cook for about 3-4 minutes, stirring often, until the beef is browned and cooked through. Remove the beef and set aside.
In the same skillet, add the minced garlic and ginger. Sauté for about 30 seconds until fragrant.
Add the broccoli florets to the skillet, stirring to combine. Cook for about 3-4 minutes until the broccoli is tender but still crisp.
Return the cooked beef to the skillet. Pour the sauce mixture over the beef and broccoli. Stir to coat everything evenly.
Cook for an additional 2-3 minutes, allowing the sauce to thicken and everything to heat through.
Season with salt and pepper to taste.
Serve hot over cooked rice if desired.