Slice the flank steak into thin strips against the grain.
In a large skillet, heat the vegetable oil over medium-high heat.
Add the sliced steak and sear for about 3-4 minutes until browned.
Remove the steak from the skillet and set aside.
In the same skillet, add the sliced onions and peppers. Sauté for about 5 minutes until softened.
Add minced garlic and cook for an additional minute.
Return the steak to the skillet.
Pour in the soy sauce and Worcestershire sauce, stirring to combine.
Season with black pepper and salt to taste.
Cook for another 2-3 minutes until everything is heated through.