Season beef strips with salt and pepper to taste.
In a large non-stick skillet over medium-high heat, add bell peppers, onion, broccoli florets and water.
Cook for 4 minutes or until tender-crisp; remove from skillet and set aside.
In the same skillet, stir-fry beef strips, garlic and crushed red pepper flakes until beef is well-browned on the outside.
Return vegetables to the skillet and add stir-fry sauce; cook and stir for 2 minutes or until mixture is heated through.
Sprinkle with peanuts and serve.