Preheat grill to medium-high heat. Brush steak with ¼ cup barbecue sauce. Add steak to grill; grill steak 4 minutes per side or to desired doneness, brushing with remaining sauce during last 2 minutes of grilling. Let stand 10 minutes before thinly slicing across the grain.
Grill corn 10 to 12 minutes or until tender, turning occasionally .
Cut corn kernels off cobs; discard cobs. Toss corn kernels with avocados and tomatoes. Serve with steak.