I never grill my sausages first, I always parboil them to cook them all the way through. I think this is the best way to grill sausage, why? Because sausage is high in fat, because it's high in fat the grease burns the outside of your sausage without cooking the sausage. Therefore, by parboiling you cook the sausage and develop a richer flavor.
Start by sauteeing the onions, garlic, garlic powder, and butter in a pot. Once they've browned, add the sausage, brown it on each side, then add the chicken broth. Boil the sausage until it's cooked all the way through (save the sausage water).
Fire up your grill, and grill the sausage on all sides to develop a medium char, no need to cook it that long. You can make a nice sauce for the sausage by taking your sausage water, some white wine, and a little bit of ketchup. Reduce it all down if you want a fancy topping for your grilled sausage.
Enjoy!