If the electric grill is a pure resistive device (a heater coil with a switch or mechanical thermostat, and perhaps an indicator light), a simple voltage-shift transformer should be sufficient.
If it contains a transformer anywhere (say, in a power supply for a digital thermostat and display panel), that transformer is probably sized for the faster switching of a 60 Hz power supply. If you drive it with 50 Hz power, you risk the primary coil of that transformer saturating, overheating, and catching fire. In this case, you'll need a converter that changes both voltage and frequency.
Other inductive loads (such as a fan motor) are anybody's guess as to how they'll behave: maybe they'll simply run slower, maybe they'll catch fire, maybe they'll blow every fuse in the building.