Melt butter in 12-inch skillet over medium heat. Cook celery, onion, carrot and bell pepper about 5 minutes, stirring occasionally, until vegetables are tender; remove from heat. Stir in cheese, thyme, 1/4 teaspoon salt and 1/8 teaspoon pepper.
Cut a deep pocket horizontally in each pork chop on the meatiest side of the bone. Fill pockets with vegetable mixture. Secure openings with toothpicks.
Heat oil in same skillet over medium heat. Cook pork in oil about 5 minutes, turning once, until light brown.
Sprinkle with 1/2 teaspoon salt and 1/4 teaspoon pepper.
Place in ungreased rectangular baking dish, 13x9x2 inches.
Cover tightly and bake 30 minutes. Uncover and bake about 30 minutes longer or until pork is slightly pink when cut near bone on the unstuffed sides of chops.