Melt 1 tablespoon of the butter in a small saucepan over medium-low heat. Add the garlic and cook, stirring, until it softens but does not brown, 1 to 2 minutes. Let cool. Then stir this garlic butter into the remaining butter in a small bowl. Stir in the parsley, olive oil, salt, and pepper.
Preheat the oven to 400 degrees F.
Rip open the baguette lengthwise, so that it opens like a book but is not ripped entirely in half. Smear the inside of the baguette with the garlic butter. Wrap the baguette in aluminum foil and bake until heated through, 10 to 12 minutes.