LtCol Onischuk was born and raised in Minnesota, and is a graduate of the University of Minnesota, Twin Cities. He commissioned in 2006 through the Platoon Leaders Course.
Upon completion of The Infantry Officers Course, he served with 1st Battalion, 5th Marines (1/5) as a rifle platoon and combined anti-armor team platoon commander. He completed two operational deployments, first with the 11th Marine Expeditionary Unit and second to Helmand Province, Afghanistan.
Following 1/5, he served as an instructor and staff platoon commander at The Basic School, followed by two years as an instructor at The Infantry Officers Course.
In 2013-2014, LtCol Onischuk attended Expeditionary Warfare School (EWS), graduating with distinction.
Following EWS, he served with 1st Battalion, 1st Marines (1/1) as a rifle company and weapons company commander, deploying as part of the Unit Deployment Program in 2014 and Marine Rotational Force – Darwin in 2016.
After service at 1/1, LtCol Onischuk served as the Marine Representative at the United States Military Academy, West Point from 2017-2019. At West Point, he received distinction as the instructor of the year within the Department of Military Instruction for academic year 2017-2018.
After West Point, he attended the School of Advanced Warfighting, graduating as the Clifton B. Cates Award Winner for the class of 2020.
His most recent tour prior to assuming command was with Third Marine Aircraft Wing, where he served as the Wing plans officer for three years.
LtCol Onischuk assumed command of the battalion on 14 December 2023.
He is a recipient of various personal awards yet is most proud of serving in units awarded the Presidential Unit Citation and Navy Unit Commendation.