Wash and cut zucchinis in half lengthwise. Remove ends. Turn zucchini halves over to skin side. Cut a 1/8" strip off of the center so vegetable will balance properly on grill grate. Don't cut too much off.
Preheat grill for medium heat.
Combine cream cheese with about 6 strips worth of bacon (reserving remainder for garnish), 1 1/2 cups of cheddar cheese, salt, garlic, onion, and black pepper. Scoop equal amounts of mixture into zucchini halves. Do not over stuff. Top with remaining cheddar cheese and bacon crumbles.
Place zucchinis onto grill grate skin side down. Close lid and cook for 8-10 minutes, or until the zucchini are tender, filling is hot, and the cheddar cheese has melted.
Remove zucchini skins from grill and garnish with chopped parsley. Serve as is, or cut into smaller pieces for appetizer portions.
Zucchini's can be cooked in the oven at 350 degrees F., for 15-20 minutes.