This paper focuses on multi-period order selection and loading problems in flexible manufacturing systems. The multi-period order selection problem is the problem of selecting orders to be produced in each period during the upcoming planning horizon, and the loading problem involves allocation of operations and required tools to machines for orders selected in each period. The objective is to minimize earliness and tardiness costs and subcontracting costs. The earliness and tardiness costs are incurred if an order is not finished on time, while subcontracting cost is incurred if an order is not selected within the planning horizon (and must be subcontracted) due to limits in processing time capacity and the tool magazine capacity of the machines. To solve the two problems simultaneously, we develop four iterative procedures in which the multi-period order selection and loading problems are solved repeatedly until a good solution is obtained. To compare the four iterative procedures, computational experiments are done on randomly generated test problems and the results are reported.