Soak wooden skewers in warm water, 10-30 minutes, before using. In a large pot, bring potatoes to a boil. Salt the water and continue to boil until potatoes are fork tender, about 8-10 minutes. Drain and cool slightly.
In a medium bowl, whisk together the oil, salt, red pepper flakes and oregano. Thread the steak, mushrooms, potatoes and tomatoes onto skewers and baste with olive oil mixture.
Heat grill to medium-high heat and grill skewers for 10-12 minutes, turning once, until meat is cooked to desired doneness. Baste skewers again before removing from the grill. Serve hot.