There are plenty of restaurants in Muscat and main towns where you can enjoy cuisin of Indian dish, Iranian dish, Turkish dish, Lebanon dish, and Chinese dish.
A lot of restaurants are located along the road and the hotels so that you need a car or a taxi to get there.
Omani foods are greatly influenced by the Indian cuisine.
You could ask your hotel to advise you about the recomended restaurants in the town.
It's not necessary to go to place such as Macdonald as you do in USA and EU when you want to eat in cheap places since Fast foods in Oman are quite pricy.
They have Mac, Kentucky, Starbucks and Costa but they are quite expensive.We recommend you to try real Omani foods rather than Fast foods.