+0

Are they both grammatically correct?

I waited outside the restaurant

I waited at the restaurant

+0

Unless they're waiting inside of course. Emotion: smile

CJ

Comments  
mosjaI waited outside the restaurant. I waited at the restaurant.

Both are grammatical.

Teachers: We supply a list of EFL job vacancies
mosjaAre they both grammatically correct?

Yes but in American English people generally say outside of.

 CalifJim's reply was promoted to an answer.