Combine the butter, garlic, cheese, parsley, salt, and pepper in a small bowl. Spread the garlic-parmesan butter over the cut sides of each bread slice.
Heat the grill to medium-high direct heat. Place the bread slices buttered-side down on the hot grill grates. Grill them for 30-60 seconds until the undersides are crispy with grill marks. Keep an eye on it because it can go from toasty to burned pretty quickly.
Flip the bread and grill for 1-2 minutes more until lightly charred around the edges.
Transfer the grilled bread to a cutting board and slice them into smaller pieces. Serve warm.
Notes
You can make the garlic butter spread ahead of time (up to a week!) and keep it in the fridge until you're ready to grill your bread.No grill? You can bake the bread in the oven for 10 to 12 minutes at 400°F.Store leftover grilled bread in an airtight container. They will keep at room temperature for a couple of days or in the refrigerator for a few days longer. I like to reheat the leftover bread in the oven or the air fryer.