This query will create an SCCM device collection from computers in an AD Organizational Unit

select SMS_R_USER.ResourceID,SMS_R_USER.ResourceType,SMS_R_USER.Name,SMS_R_USER.UniqueUserName,SMS_R_USER.WindowsNTDomain from SMS_R_User where SMS_R_User.UserOUName = "contoso.com/OU1/SubOU/Users"

Replacing the name of the OU with your own.