1Cut the zucchinis down the middle (the long way) and scoop out about 2/3 of the meat. This should create the "boat" so that future ingredients will be cradled in the zucchini. Put all parts of the zucchini aside.
2Cook the sausage until 3/4 of the way done and then remove from heat into a large mixing bowl.
3Combine the sausage, red pepper, yellow pepper, yellow squash and tomatoes with the dry ingredients.
4Take the zucchini that you scooped out of the "boat" and mix with the garlic. (Keep this seperate from the sausage.)
5Place some croutons into the shell and then scoop some of the sausage mix on top of the croutons.
6Then put some of the zucchini and garlic mix on top of that, followed with some more croutons.
7The last thing to go on would be the slices of onion. Using a sheet of foil, spray it with non-stick vegetable spray and wrap it around the zucchini.
8Set on the grill, not on direct flame or heat.
Cook until tender.