In many AH's, from Cliveless World to random maps, the Ottoman Empire is sometimes shown as to control the entire Arabian peninsular. Is that even possible? In its later years it had enought trouble with controlling the Turks themselves, so how could they come to directly rule over all of Arabia?
The Ottomans didn't have much trouble controlling anyone in the core areas of the Empire, especially Anatolia and Syria/Palestine. It was difficult to control areas with significant foreign-sponsored Christian communities in outlying areas like Eastern Anatolia, and fringe areas largely populated by nomads.
Arabia was from around 1870 at least nominally controlled by the Ottomans. The Saudis were vassals and officially Ottoman governors, and the other major power, the Rashidis, were more intimately involved with the Ottomans. In an ATL, once the Baghdad Railway is completed, there is a direct route from Istanbul to the Gulf, and that, coupled with the Hijaz RR, would have greatly magnified Ottoman power-projection capabilities into Arabia. The Hijaz and Hasa (the coastal strip on the Persian Gulf) are where all the food, water, and access to trade are, so secure control of these makes the interior relatively dependent and harmless. It wouldn't be overnight, but if the empire had survived the interior would have been integrated.