Place peppercorns in a small zip-top plastic bag; seal. Crush peppercorns using a meat mallet or small heavy skillet. Combine peppercorns, salt, and garlic in a bowl; rub evenly over steaks.
Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add steaks to pan. Reduce heat; cook 4 minutes on each side or until desired degree of doneness. Remove steaks from pan. Cover and keep warm.
Add port and broth to pan, stirring to loosen browned bits. Cook until reduced to 1/4 cup (about 3 minutes). Place 1 steak on each of 4 plates; drizzle each serving with 1 tablespoon sauce. Sprinkle each serving with 3/4 teaspoon thyme.