Preheat the oven to 350 degrees F. Slice the tops off of the garlic bulbs so that the tip of each clove is exposed. Drizzle garlic cloves with olive oil and wrap in foil. Place on a baking sheet. Bake for 30 minutes, or until garlic is soft. Remove garlic from oven, unwrap from foil, and let cool on wire rack for 5-10 minutes, or until cool enough to handle.
Set the oven to broil. Slice the loaf of bread in half horizontally, and place cut side up on a baking sheet.
Squeeze the cloves of garlic from their skins into a medium bowl. Stir in the butter, parsley, and Parmesan cheese until well blended. Spread onto the cut sides of the bread.