In 1998, Oleg Kosmenyuk graduated from Pavlodar State University, named after S. Toraigyrov (Kazakhstan), majoring in thermal power engineering.
From 1991 to 1996, he worked at Ekibastuzskaya GRES-1. From 1997 to 2008, he worked in AES Power Corporation in Kazakhstan where he became Regional H&S Director before leaving the company. From 2008 to 2011, he was General Director of Maykuben West LLP of Kazakhmys Corporation. From 2011 to June 2013, he was Power Plant Operation and Maintenance Manager at Reftinskaya GRES bearing full responsibility for the power plant performance. From June 2013 to April 2016, he was Vice President - Head of Coal Generation - Director of Reftinskaya GRES.
Since April 2016, Oleg Kosmenyuk has held the office of Deputy General Director - Head of Generation in PJSC Enel Russia.