If needed hinly slice the sirloin steak, slicing across the grain of the meat. Add the teriyaki sauce and marinade for at least 30 minutes, ideally overnight.
Cook rice, as directed.
Heat the canola oil over high heat in large skillet or wok. Add the beef slices with marinade and brown on all sides, tossing often. Saute over high heat for 5 minutes. Transfer the beef and sauce to a plate.
Saute the bell pepper slices and broccoli in the same skillet for 4 to 6 minutes, or until bell pepper has softened and broccoli turns brighter green.
Add the beef and sauce back into the skillet and toss together. If needed, thicken the sauce with a cornstarch slurry (1 Tbsp cornstarch mixed into 2 Tbsp water). Let simmer for a few minutes and then serve.
Serve Teriyaki Beef & Veggie Stir-fry over sticky white rice with optional sesame seed garnish.