Cut the French bread in half lengthwise, making 2 equal pieces. Place bread cut side up on a large baking sheet.
In a medium-size bowl, mix all of the cheeses, mayonnaise, and chopped green onion together. Set aside.
Mix the softened butter and garlic together in a small bowl. Spread the butter evenly all over the two halves of bread. Top each loaf evenly with the cheese mixture; spreading out evenly.
Bake for 10 minutes, or until the cheese is melted and bubbly. Carefully remove from oven and let stand a few minutes. Slice, serve and enjoy!