65 ILCS 5/11-13-3.1

In municipalities of less than 500,000 inhabitants no change shall be made in the zoning ordinance nor shall any zoning variation be granted within 6 months after the date upon which an official plan is adopted by the corporate authorities unless such change in the zoning ordinance or such variation is approved by a two-thirds vote of the corporate authorities or the zoning board of appeals then holding office, as the case may be.