https://www.associatedcontent.com/article/5872292/companies_granted_waivers_to_opt_out.html
https://www.usatoday.com/money/indu...-07-healthlaw07_ST_N.htm?loc=interstitialskip
McDonald's offers their part time and hourly workers a "mini-med" plan. It only covers general practitioner visits and scripts. By law they are not required to offer any health insurance to part time employees. Under Obamacare, McDonald's is required to offer full health care insurance if they are going to offer insurance. It is cheaper for McDonald's to drop the health insurance for part time employees.
The administration determined, and rightfully so, that these part time employees will be better off with a mini-med plan than no plan at all so they exempted McDonald's. Basically any large corporation that employs numerous part time employees such as fast food restaurants, convenience stores such as 7-11, etc. will benefit from an exemption.