Marchuk, who named education minister in May 2012, told the premier that he wants to continue working in education, but not in the lead role.
Marchuk says the government's education agenda is entering a crucial period that will require significant resources and he feels he can't provide that.
The premier says Labour Minister Don Morgan will also become education minister.
Marchuk will be the new legislative secretary to education minister.
Rob Norris will take over Morgan's duties as advanced education minister, a role Norris held before the last cabinet shuffle.