Traditional:
* A bag of oranges
* A pile of oranges
* A basket of oranges
* A box of oranges
More poetic:
* A grove of oranges (for a large number of trees)
* A blush of oranges (for a vibrant display of the fruit)
* A burst of oranges (for a sudden abundance)
Informal:
* A bunch of oranges
* A heap of oranges
Ultimately, the best collective noun to use depends on the context and the desired tone.