In a large skillet, saute onions in oil and 1 tablespoon butter until softened. Reduce heat to medium-low; cook, stirring occasionally, for 30 minutes or until deep golden brown.
Meanwhile, cut roast into 1-1/2-in. cubes; sprinkle with salt and pepper. In a large skillet over medium heat, brown beef in batches in remaining butter.
Transfer beef to an ungreased 15x10x1-in. baking pan; top with onions and blue cheese. Bake at 350° for 8-10 minutes or until beef reaches desired doneness (for medium-rare, a thermometer should read 135°; medium, 140°; medium-well, 145°). Insert skewers into appetizers.