It will depend of your horses ...
Most of the time, horses can share a pasture after establish the hierarchy but some will never tolerate each other.
I think you have to try, and you have to remenber that the firsts moments could be violent but as long there is no blood it's kind of OK to let them together.
I hope I don't make to much mistakes, I haven't practice my wroten english since a while !
Join the fun and sign up to connect with our 200,000 members!