Creating the 15-Minute Steak Stir Fry is straightforward. Follow these steps to whip up this delicious meal:

1. Prepare the Ingredients: Begin by slicing the flank steak thinly against the grain. This ensures tenderness when cooked.
2. Marinate the Steak: In a bowl, combine the soy sauce, oyster sauce, cornstarch, and water. Add the sliced steak and let it marinate for about 5 minutes while you prepare the vegetables.
3. Heat the Pan: In a large skillet or wok, heat the vegetable oil over medium-high heat until shimmering.
4. Add the Steak: Once the oil is hot, add the marinated steak to the pan in a single layer. Sear for about 2 minutes until browned, then flip and cook for an additional minute. Remove the steak from the pan and set aside.
5. Stir-Fry the Vegetables: In the same pan, add the sliced onion, bell peppers, and broccoli. Stir-fry for about 3-4 minutes until the vegetables are tender-crisp.
6. Add Aromatics: Stir in the minced garlic and ginger, cooking for an additional 30 seconds until fragrant.
7. Combine Steak and Vegetables: Return the cooked steak to the pan and mix everything together for another minute to heat through.
8. Season: Taste and adjust the seasoning with salt and pepper as needed.
9. Serve: Remove from heat and serve immediately over cooked rice or noodles.

These steps will guide you through creating this incredible dish effortlessly!