Heat oven to 375°. Heat oil in 10-inch nonstick skillet over medium-high heat. Cook frozen bell pepper mixture and celery in oil 3 to 4 minutes, stirring occasionally, until tender. Stir in parsley; remove from skillet. Cover to keep warm.
Mix pork, chili sauce, garlic salt, thyme and red pepper. Shape mixture into 4 oval patties, 1/2 inch thick. Cook patties in hot skillet over medium heat 8 to 10 minutes, turning once, until no longer pink in center.
Place buns, cut sides up, on ungreased cookie sheet. Bake 3 to 5 minutes or until toasted. Serve patties on buns topped with vegetables.