Well I started going to Boundary Park in 1958. Latics were sitting at the bottom of League Division Four applying for re-election. Teams weren't automatically relegated out of the Football League as they are now. They relied on their 'friends' - all the other teams - to vote for them to stay in the league.
Regarding away supporters, I think they congregated in the Rochdale Road end, but there was no segregation. I know because me and my dad always watched from that end. When Latics played Liverpool in the FA Cup, the whole of the Rochdale Road end was given to their fans. These were the days when at half time the supporters changed ends to give their support to their team - how quaint it all seems now.
Boundary Park ground was in a better state than the Broadway stand is now! But the main stand, top tier is much the same as it was - cramped wooden seats! Toilet facilities are still much the same as they were, although I don't remember soap and paper towels. The main difference is that everyone stood, with barriers positioned every few yards. In front of the main stand was standing (this is where I watched the Liverpool match) and in front of the broadway stand.
The match against Liverpool was much anticipated by all Oldham fans. We had a really good team with players like Bobby Johnstone and Bert Lister in our forward line. We had beaten Chesterfield and Bristol Rovers, who were then two divisions above us in the League. The attendance was recorded at 42,000 but it is thought that many more managed to get in for nothing! We had been used to 14,000 gates, pretty good in the fourth division, but when I got to the ground and saw all these people it quite took my breath away. And once in the ground all the fans were tightly packed in. One of my friends was offered a decent amount to part with his ticket to a Liverpool fan but he didn't sell. There was great excitement at seeing Liverpool in the flesh, a team although at the top of the second division, filled with well known players. Ian St John, Roger Hunt - the basis of the team that not only won promotion that season but two years later won the League. Latics had a goal by Lister disallowed for offside - it was plainly onside - we could see because the action happened at the other end of the pitch!! Ian St John scored two goals for Liverpool and Colquhoun replied for Latics. One of St John's goals hit the underside of the crossbar bounced down and out but the ref said it had crossed the line. But Latics gave a really good account of themselves and we all went home saying we wuz robbed, like you do. Hope this is helpful. If I can give further help my email is petelatics@hotmail.com