Prepare the Beef: Thinly slice the steak against the grain. Season with salt and pepper.
Cook the Vegetables: Heat oil in a large skillet or wok over medium-high heat. Stir-fry bell peppers and onion for 3-4 minutes, then add minced garlic and cook for 30 seconds. Remove the vegetables from the skillet.
Cook the Beef: Add a little more oil if needed and cook the sliced beef for 3-4 minutes, stirring occasionally, until browned and cooked through.
Make the Sauce: In a small bowl, mix together soy sauce, oyster sauce, sugar or honey, and crushed red pepper flakes.
Combine Everything: Add the vegetables back into the skillet with the beef, pour the sauce over the top, and stir to combine. Cook for another 1-2 minutes until the sauce thickens slightly.
Serve and Enjoy: Serve the pepper steak over steamed rice or noodles.
