1. Place onion and bell pepper slices in a large resealable plastic bag. Add vinegar, olive oil, Worcestershire, soy sauce, garlic, rosemary, and pepper. Add steak, coat with the marinade, squeeze out excess air, and seal the bag. Marinate in the refrigerator for at least 3 hours, or overnight.

2. Remove steak from the marinade and shake off excess. Discard 1/2 of the liquid marinade.

3. Pour the remaining liquid plus the onion and pepper slices into a large frying pan. Cook over high heat for 2 minutes. Move vegetables to the side of the pan and add steak. Reduce heat to medium-high and cook for 4 minutes. Remove vegetables to a plate and flip steak; cook until steak is beginning to firm and is hot and slightly pink in the center, about 3 to 5 more minutes. An instant-read thermometer inserted into the center should read 140 degrees F (60 degrees C) for medium doneness.

4. Drain liquid from the pan. Serve steak with onion and bell pepper.

Editor's Note:

Nutrition data for this recipe includes the full amount of marinade ingredients. The actual amount of marinade consumed will vary.