Press gently on the lid of the panini grill so you won't squeeze out the filling.
Spread peanut butter evenly on cut sides of bottom halves of bagels; spread jelly evenly on cut sides of top halves of bagels. Place top halves of bagels on bottom halves, jelly sides down.
Brush bagels lightly with melted butter; cook in a preheated panini press 2 minutes or until lightly browned and grill marks appear. Serve immediately.
Note: Sandwiches may also be cooked in a grill pan. Cook 2 minutes on each side or until lightly browned and grill marks appear.