Yes, but it will take 50% longer. It's best to completely defrost meat and poultry before grilling so it cooks more evenly. However, uniformly thin meat, such as frozen hamburger patties, may be grilled frozen.
Remember that outdoor grills can vary in heat. Use a food thermometer to check for safe cooking and doneness of meat, and take the temperature in several places to ensure even cooking. For the safe internal temperate of meat and poultry please visit Is it Done Yet?