The academy graduate has suffered with illness and a shoulder problem in the early part of the season, but insists that he is back to full fitness now.
Osborn played for the entire 90 minutes of Forest's highly impressive 1-0 win over Birmingham City on Tuesday, and the midfielder was delighted to be involved.
“I felt like my old self again for the first time this season, including pre-season. I’ve been in a battle to get my fitness back," he said on the club's official website.
“I had a shoulder problem and then a bad case of food poisoning, from which I lost a lot of weight. I just couldn’t really seem to put it back on. I felt energy-less. But in the last week of training, and tonight, I felt back to normal.”
Osborn's return to fitness adds to the options available to Forest, and gives Dougie Freedman greater depth to his squad.
The 21-year-old enjoyed a fine breakthrough season in 2014/15, making 40 appearances and scoring three times, as he arguably became one of the Reds' most consistent performers.
Osborn will now be hoping to build on that campaign, but he faces increased competition for places in the starting line-up this term.
Forest have added considerable quality to their squad over the summer, and Osborn will need to ensure that he is at the top of his game if he is to stay in the first XI.