In a large skillet or wok, heat the vegetable oil over medium-high heat.
Add the sliced onion and sauté for 2-3 minutes until softened.
Add the ground beef to the skillet. Cook, breaking it apart with a spoon, until browned, about 5-7 minutes. Drain excess fat if needed.
Stir in the minced garlic and ginger, cooking for an additional minute until fragrant.
Add the broccoli florets and cook for 3-4 minutes until they are bright green and slightly tender.
In a small bowl, mix the beef broth, soy sauce, oyster sauce, and cornstarch together. Pour this mixture over the beef and broccoli.
Stir well and let it simmer for another 3-4 minutes, or until the sauce thickens.
Season with salt and pepper to taste.
Serve the stir-fry over cooked rice or noodles.