Preheat oven to 375 degrees
Combine all ingredients (besides zucchini) in a large bowl, gently, until combined well.
Scoop mixture into zucchini halves.
Place zucchini boats on a flat sheet pan. (I first lined pan with parchment)
Bake in your preheated 375 degree oven for about 15 minutes, or until hot throughout.
If topping with cheese; do so during the last 4 minutes of cook time.
These would also be great on the grill!