At the moment i see no way to express that via OQL. It also seems to be an Oracle specific extension of SQL.
Using LINQ, you could emulate this behavior by using
.OrderBy(x => x.Property != null ? 0 : 1).ThenBy(x => x.Property)
OpenAccess ORM is now Telerik Data Access
. For more information on the new names, please, check out the Telerik Product Map