About 400 firefighters from across the state opposed the plan during a rally earlier this week outside the state Capitol.
Fallin has said the state spends $80 million to $100 million each year to administer the pensions and the state could realize at least 15 percent in savings by consolidating the pension plans.
Miller, who also serves as chairman of the Oklahoma State Pension Commission, said the proposal would not change any benefits promised or currently being received, but is intended to reduce administrative expenses.
“We value our firefighters, police, teachers and all public servants, and want to honor their service by providing them a secure and solvent pension fund,” he said. “The firefighter's pension plan is the second-worst-funded of the state's seven pension plans despite receiving the highest percentage of dedicated state funding, has the lowest five-year investment returns, and pays the second-highest investment fees for those returns. Clearly, the plan can do better and we are working hard to improve it.”