English
Go for an outing OR on an outing. To me the both look fine. English speakers also say this ( on sites for discussions)but can I use both?

Question

Answer

Both are correct and natural.

For more explanation:

"For" indicates purpose.

I am going to the store for milk.
I am going for milk.

"On" indicates an excursion.

I am going on a fishing trip.
I am going on a hike.

"going verb-ing" indicates an outdoor recreational activity of variable duration.

I am going hiking.
I am going camping.
I am going swimming.
I am going bicycling.

special case - I am going shopping.  [correct and common]