The company plans to add two pollution control devices, dubbed scrubbers, to the coal-fired units at the Sooner Power Plant near Red Rock,
It will convert two coal-fired units at the Muskogee power plant to natural gas and upgrade the units at the facility.
The existing natural gas steam units were first installed in the late 1940s and the new turbines will better support both reliability and efforts to reduce customer energy costs.
OG&E VP of public affairs and corporate administration Paul Renfrow said: "The Mustang plant site has all of the necessary infrastructure, the workforce and the necessary environmental permits.
"It only makes sense to modernize this plant so it can provide several more decades of use rather than spending more money to locate the combustion turbines at a different site."
The company is also seeking approval to recover the costs associated with its compliance and Mustang modernization efforts that are estimated to be about $1.1bn by 2019.
OG&E, a subsidiary of OGE Energy, serves over 810,000 electric customers in Oklahoma and western Arkansas.
