Prepare a grill to medium-high heat.
Cut the potatoes into steak-sized fries. Blanch them in boiling water for 2 to 3 minutes. Submerge in an ice bath to stop the cooking. Dry the potatoes and coat with the olive oil. Grill until the fries are crispy and golden, 15 to 20 minutes. Season with Cajun seasoning and salt, to taste. Serve hot.