Securing travel for those under 19 and an expansion of the scheme the following year, the Scottish Greens negotiated the initiative in pre-budget deals in the last parliamentary session.
The new project will go live in January after a Covid-related delay.
The Net Zero, Energy and Transport Committee will be asked to approve subordinate legislation to impose the change on Tuesday, clearing the way for the start of the scheme.
"This important policy takes a vital step forward today as it clears a parliamentary hurdle," said Green transport and climate spokesman Mark Ruskell.
"Free bus travel for young people is not only a transformational policy in terms of family budgets and opening up opportunities for young people, it can help shift people out of car use and help tackle the climate emergency.
"What's more, as we recover from the pandemic, this policy will be vital in encouraging people back on to public transport safely to ensure we have a green recovery.
"The Scottish Greens believe public transport should be free at the point of use and serve all our communities, and January will see a major step forward to this aim."
The news of free bus travel comes after legislation was approved by the Scottish Parliament in March 2021 which allowed 5-18 year olds resident in Scotland to access free bus travel through the National Entitlement Card (NEC) and the Young Scot branded NEC.