Clean the beef and thinly slice. Season with salt and pepper; set aside. Slice onion, and peppers and set aside.
Heat oil in a pan/skillet/wok (you can use a few tablespoons of oil if you desire). Add the sliced beef on a single layer and cook/sear for 4-5 minutes (depending on the thickness and the type of beef you're cooking with) on both sides until it is almost cooked. Remove the beef and set it aside.
Clean the pan with paper towels, heat the remaining oil over medium heat, add the sliced onion, ginger, and garlic. Sauté for about one-minute stirring and you cook, add the sliced bell peppers (I used red and green) and cook for about one minute.
Add the remaining vegetables you're using and combine, cook until slightly soft.
Transfer the cooked beef, and some of the sauce (depending on how much sauce you want), combine, you can crank up the heat and stir fry until hot.
Adjust the seasonings as necessary.
Serve and enjoy with your favorite side dish.
Sprinkle sesame seeds (if desire), and enjoy.