Making 15-Minute Sheet Pan Beef and Broccoli is straightforward. Follow these steps for a delicious outcome:

1. Preheat the Oven: Set your oven to 425°F (220°C) to start heating while you prepare the ingredients.
2. Prepare the Marinade: In a small bowl, mix the soy sauce, oyster sauce, minced garlic, grated ginger, and cornstarch. Set aside.
3. Slice the Beef: Thinly slice the flank steak against the grain for tender pieces.
4. Combine Ingredients: In a large bowl, toss the beef slices and broccoli florets with olive oil, salt, and pepper until well-coated.
5. Add Marinade: Pour the marinade over the beef and broccoli, mixing well to ensure even distribution.
6. Spread on Sheet Pan: Arrange the beef and broccoli mixture on a large baking sheet in a single layer for even roasting.
7. Roast in the Oven: Place the sheet pan in the preheated oven. Roast for 10-12 minutes, or until the beef is cooked through and the broccoli is tender-crisp.
8. Check for Doneness: Use a meat thermometer to ensure the beef reaches a minimum internal temperature of 145°F (63°C).
9. Serve: Remove the pan from the oven and let it cool slightly before serving.
10. Garnish: Sprinkle with sesame seeds and sliced green onions for added flavor and presentation.

Following these steps will ensure you create a delicious, savory 15-Minute Sheet Pan Beef and Broccoli that will have everyone asking for seconds!