Take grates out and covers, spray with oven cleaner and put in a dark plastic bag. Leave in sun all day and just wash off with outside hose. It's so great and easy. You can spray inside with oven cleaner, wait awhile and scrape off.

Will this work with the oven racks also?

Yes it will! I not only do this for the grates but I did it for the whole grill! Just make sure you wash with warm, soapy water before adding lighter fluid!

Thanks. Will try after the holiday cookout!