Drain cannellini beans from liquid and place in a pan with three tbsp. olive oil. Stir over low heat adding salt and pepper to taste. Cook beans until heated and keep warm.
If using an outdoor grill, prepare charcoals and let burn until covered with white ash. If using a gas grill, preheat on high heat. Brush the grill rack with oil.
Season the steaks with salt and pepper. Place the steaks on the rack and grill until the meat is brown and seared on the outside and rare in the center, 15-18 minutes in total, or 18-22 minutes for medium.
Transfer the beans to a serving bowl and sprinkle with thyme. Arrange a bed of arugula on a platter. Slice the steaks into thick slices and place over the arugula. Sprinkle with salt and pepper. Place lemon wedges around the platter, and offer beans on the side.