In the U.S. armed forces, "CQ" stands for charge of quarters. Service members in this position are in charge of monitoring all traffic in and out of a barracks.
CQ is made up of two members: a non-commissioned officer and an enlisted service member. Shifts typically last for 24 hours, during which service members are not allowed to sleep or consume alcohol. During the assignment, CQ duties may include sweeping and cleaning the barracks entryway and restroom as well as completing radio checks every few hours with other barracks and battalion headquarters around the base.
Those on duty may also be responsible for checking to ensure that service members are in their rooms after curfew. CQ members are excused from their duties after they are relieved by a senior non-commissioned officer.