Season the steak with salt and pepper. Rub all over with the garlic and drizzle with EVOO. Let sit for 15 minutes at room temperature. (Discard the garlic.)
Preheat a grill to medium-high. Wrap the tortillas in foil and place over indirect heat until warm, about 10 minutes. Oil the grill grate and grill the corn, covered and turning occasionally, until blistered, about 5 minutes. When cool enough to handle, slice off the kernels and transfer to a salad bowl.
Grill the steak, turning halfway through, for about 5 minutes for medium-rare. Let the meat rest for 10 minutes before thinly slicing.
Add the avocados, radishes and onion to the corn. In a small cup, whisk together 2 tbsp. EVOO, the lime zest and 3 tbsp. lime juice; season with salt and pepper. Add to the salad and toss. Serve with the steak and tortillas for wrapping.