Heat closed contact grill 5 minutes. Spread one side of each slice of bread with pesto. On 2 slices of the bread, layer beef, roasted peppers and cheese; top with remaining slices of bread, pesto side down. Brush outside of sandwiches with butter.
When grill is heated, place sandwiches on bottom grill surface. Close grill; cook 3 to 5 minutes or until bread is toasted and cheese is melted.