Slice your beef thinly against the grain for tenderness, and chop your bell peppers and onion into thin strips. Mince the garlic and ginger.

In a large skillet or wok, heat the vegetable oil over medium-high heat.

Add the sliced beef to the skillet in a single layer. Let it sear for about 2-3 minutes without stirring, then stir and cook for another minute until just cooked through. Remove the beef from the pan and set it aside.

In the same skillet, add a little more oil if needed and toss in the sliced onion and bell peppers. Sauté them for about 3-4 minutes until tender but crispy.

Add the minced garlic and ginger to the vegetables, stirring for about 30 seconds until aromatic.

Return the seared beef to the skillet, combining with the vegetables.

Drizzle the soy sauce and oyster sauce over the mixture, stirring to coat everything evenly. Let it cook for another 2-3 minutes.

Taste your stir-fry and add a pinch of salt and black pepper to enhance the flavors.

Serve hot over a bed of rice or noodles.