Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat. Add the sliced beef and stir-fry for about 2-3 minutes until browned. Remove the beef from the pan and set aside.

In the same skillet, add the remaining tablespoon of oil. Add the minced garlic and ginger, and stir-fry for about 30 seconds until fragrant.

Add the bell pepper, broccoli, and carrot, and stir-fry for another 3-4 minutes until the vegetables are tender-crisp.

In a small bowl, mix together the oyster sauce, soy sauce, cornstarch, water, sugar, and black pepper. Pour the sauce over the vegetables in the skillet, stirring to combine.

Return the cooked beef to the skillet and cook for an additional 2-3 minutes until everything is heated through and the sauce has thickened.

Serve the beef with oyster sauce over cooked rice.