Ingredients: 

1 1/2 pounds boneless beef sirloin steak
1/3 cup red wine vinegar
1/4 cup ketchup
2 tablespoons orange juice
2 tablespoons soy sauce
1 tablespoon Worcestershire sauce
1 teaspoon Dijon-style mustard
1/2 teaspoon garlic powder
1 teaspoon salt
1/2 teaspoon freshly ground pepper
3 oranges, peeled and sectioned
1 large green bell pepper, cut into 1-inch squares
1 large red or white onion, cut into 1-inch wedges, separated