Preheat oven to 425°.
Place bread in a food processor; pulse 10 times or until coarse crumbs measure 1 cup. Combine breadcrumbs and next 4 ingredients in a shallow dish. Dip meaty side of lamb racks in egg whites; dredge in breadcrumb mixture. Pat any remaining breadcrumb mixture onto rack.
Place lamb, meaty side up, on a broiler pan coated with cooking spray. Insert meat thermometer into thickest part of lamb, making sure thermometer does not touch bone.
Bake at 425° for 45 minutes or until thermometer registers 145° (medium-rare) to 160° (medium). Let stand 10 minutes before slicing.