In a bowl, cover steak with soy sauce, oyster sauce and garlic. Cover and let marinate for several minutes. If you marinate for up to 8 hours the flavors will develop.
In a wok or large skillet on medium-high, heat 1 tablespoon oil for one minute. Add steak with marinade for 2-4 minutes until cooked through. Place in clean bowl and cover.
Add 2 Tablespoons oil to wok and heat for one minute. Add broccoli, onion, yellow pepper, chili pepper and mushrooms. Stir fry for 2-4 minutes. Add beef and stir fry for one minute to reheat.
Serve over brown or white rice.