Seasoning:
2 tablespoons olive oil
1 tablespoon chopped fresh oregano or 1 teaspoon dried oregano leaves
2 cloves garlic, minced
1/2 teaspoon ground black pepper

Cucumber-Yogurt Sauce:
1/2 cup plain yogurt
1/3 cup finely chopped seeded cucumber
2 tablespoons crumbled feta cheese
1 clove garlic, minced
1/4 teaspoon ground black pepper
1/8 teaspoon salt

Instructions

Cut beef steak into 1-1/4-inch pieces. Combine seasoning ingredients in large bowl. Add beef, mushrooms and bell pepper pieces; toss to coat.2.Alternately thread beef and vegetable pieces evenly onto eight 12-inch metal skewers, leaving small spaces between pieces.3.Place kabobs on grid over medium, ash-covered coals. Grill kabobs, covered, 8 to 10 minutes (over medium heat on preheated gas grill, 9 to 11 minutes) for medium rare (145°F) to medium (160°F) doneness, turning once. Season kabobs with salt, as desired.4.Meanwhile, combine sauce ingredients in small bowl. Serve with kabobs.

Cook's Tip:  Eight 12-inch bamboo skewers may be substituted for metal skewers. Soak bamboo skewers in water 10 minutes before using; drain.

Cook's Tip:  To broil, place kabobs on rack in broiler pan so surface of beef is 3 to 4 inches from heat. Broil 9 to 12 minutes for medium rare (145°F) to medium (160°F) doneness, turning once. 

source:  http://beefretail.org/imagesrecipes.aspx