Cut pears in half and core them. Peel one pear half, cut into chunks and place in blender with red wine vinegar, Dijon mustard, salt and pepper. Puree until smooth. With machine running, slowly pour in olive oil; set aside.
Cut remaining (unpeeled) pear halves into 14-inch slices and place in a large bowl with frisee, radicchio, cheddar cheese and pecans. Drizzle with dressing and toss gently; serve immediately.