Caretaker boss Dean Holden could not fault the effort from his players yesterday but luck is not with his side at the moment.
Lewin Nyatanga had given Barnsley the lead before Conor Hourihane extended their advantage through a fluke goal which rebounded into the back of Jake Kean's goal from Carl Winchester's clearance.
Mike Jones pulled a goal back just before half with a wonderful strike but Nyatanga scored his second in the second half to seal the game for the Tykes.
Speaking about the game, Holden admitted: "It's a bad result considering the way the game went.
"We were in it for half an hour and there was nothing between the teams but it was again a poor goal and it gave them a lift. We've had the best chances in the game and Jake's not made a save in the game but we've conceded three goals from three set pieces.
"We work on them extensively. It becomes a one v one battle on a set piece. You can organise each other on the pitch but when the ball is in the air you have to have the desire to win the one v one battle, and once it goes beyond you, and Jake makes a save like he did for the first one, you make sure you're in the right position to clear the ball but unfortunately at the moment we are not doing that.
"You can't feel sorry for yourself. We have had some good chances today. The lads have given everything, there is no question at all about commitment and playing for each other but goals change games and they had a lift towards the end but we just need to get that first goal and give ourselves a lift. When your are conceding goals like we are, it is tough to win games.
"It was a great strike from Jones again. He is producing for us at the moment but unfortunately it wasn't enough to get us something on the day."
Asked whether the decision to send Adam Lockwood was a harsh one, Holden responded: "Yes. It's the referee's decision and it's not for me to comment on but I don't think Locky can get out the way.
"The referee said to me after the game he [Lockwood] had time to look at him and step across into his path. It's a bad decision but that's not the reason why we lost the game by any stretch of the imagination. That will now be another suspension for Tuesday."
The 35-year-old reserved special praise for the Oldham supporters who turned up in their numbers and made it an intimating atmosphere all afternoon.
"They were fantastic," Holden said. Barnsley brought however many thousand supporters and it started off a good atmosphere but you didn't hear them for the rest of the game but our fans out sung them all afternoon which is great to see.
"Adversity brings out the best in everyone and I think the fans can feel that. We are up against it at the minute and they got right behind the lads and we are all thankful for that support."
Watch the full interview on Latics Player.