Wash and chop your vegetables. Cut the bell peppers into strips, and break the broccoli into small florets. Slice the beef thinly against the grain.

In a bowl, combine the sliced beef with soy sauce, oyster sauce, and a dash of sesame oil. Let it marinate for 15 to 30 minutes.

Heat a large skillet or wok over medium-high heat. Add vegetable oil and let it get hot. Add the marinated beef in a single layer and cook for 3 to 4 minutes, stirring occasionally.

In the same pan, add more oil if needed. Toss in the minced garlic and grated ginger, stirring for 30 seconds until fragrant. Add your prepared vegetables and stir-fry for 5 to 7 minutes.

Add the cooked beef back into the pan with the vegetables. Stir well to combine all the flavors and cook for another 1 to 2 minutes.