Hi Toga,
No, for 350 RO you can only find a small appartment. Muscat is becoming very expensive for housing. There is a very big availability problem so prices rise higher and higher.
It depends what you're looking for. I'm in an area close to the airport but further away from all the activities. I pay 450 RO but for this amount I have a very nice villa of 250 mē. If you want to stay in one of the favourite expat area's like MSQ you find for the same money a small studio but you have everything (except airport!) close by.
Greetz,
Seb