In a small bowl, whisk together the soy sauce and cornstarch. Set aside.
Heat 1 tablespoon of vegetable oil in a large skillet or wok over high heat. Add the sliced steak and cook until browned, about 3 to 4 minutes. Remove the steak from the skillet and set aside.
Add the remaining 1 tablespoon of oil to the skillet. Add the sliced bell peppers and onion, and stir-fry for 4 to 5 minutes until crisp-tender.
Stir in the minced garlic and ginger, and cook for an additional 1 minute until fragrant.
Return the cooked steak to the skillet. Pour the soy sauce mixture over the steak and vegetables. Stir well and cook for 1 to 2 minutes until the sauce thickens and coats the ingredients.
Remove from heat and serve immediately.
Notes
Serve hot over a bed of steamed rice or noodles for a complete meal.