I cant comment on a quaker but I have two greys.
When I got Keeko at 12 weeks Charlie would have been about a year old.
They were both in the same room together with their cages at the opposite sides of the room. This gave them time to accept each other being there and generally watch each other.
I started letting them out seperately for a while but found they would try to go to each others cages.
The first time I let them out together I was so nervous, there was an awful lot of beaking going on (this went on for a while) which I was told by an experienced member here they were trying to see who was the alpha male!
I would let them out together for ten minutes at a time (supervised at all times) then gradually increased this.
Months on, my boys are out together most of the day now, they play together and also have squabbles, they sit and preen each other and regurg for each other, I believe its the best thing I could have done!
On a bad note, there is twice the mess!