The group of 15-18 clients meet at the centre three days a week, taking part in activities such as swimming, soccer and arts and crafts.
Mrs Penn said the Christmas tree project had been a team effort, which everyone had contributed to and was proud of.
Occupational therapist Alexandra Jensen said Step Ahead was incredibly valuable to the clients' rehabilitation.
"Without it they would have very dull days ... this is the stimulation in their week," she said.
With the tree done, the group are now making Christmas baskets and baking gingerbread and other sweet treats to go in them.
Client Missy Henry said she was looking forward to the group's Christmas barbecue next week, when they remove the edible treats from the tree.
"I'm looking forward to the candy canes and chocolate," she said.
They will also enjoy a special Christmas lunch at Skyline tomorrow.
"If they aren't celebrating at home they have at least celebrated here," said Mrs Jensen.
Staff said community support had been amazing, with Bunnings donating the laminate the tree was made of, Don and Peter from the Menz Shed cutting it out and other local businesses donating materials throughout the year. Client Alan Goldsack, an ex-engineer, also did a great job measuring up the tree, they said.
Mrs Penn said the tree, minus its few candy canes, would be kept and added to next year to make it into a "multi-dimensional" tree.