Combine butter and garlic powder in bowl.
Spread 1 side of each bread slice with about 1 teaspoon garlic butter.
Assemble sandwiches by topping 1 bread slice, buttered-side down, with 3 cheese slices. Place 1 bread slice, buttered-side up, over cheese.
Heat 12-inch skillet or griddle over medium heat.
Place 2 sandwiches into skillet; cook, turning once, 4-6 minutes or until golden brown and cheese is melted. Repeat with remaining sandwiches.
For flavor variety add 1/2 teaspoon dried Italian herbs to the butter mixture.