Heat oven to 425. Spray jelly roll pan, 15 1/2 x 10 1/2 x 1 inch, with cooking spray. Mix breadcrumbs, cheese, oregano, garlic salt and pepper. Spread mustard on all sides of breasts. Cover mustard-coated chicken breasts with breadcrumb mixture. Place chicken breasts in pan. Bake uncovered about 25 minutes or until juice of chicken is no longer pink when centers of thickest pieces are cut.