Combine all marinade ingredients except steak in a large zip bag. Seal and squish to combine.
Add the steak, squeeze out the air, zip the bag closed and massage the marinade into the steak a bit. Refrigerate the steak and lie it flat in the refrigerate. Let it marinate for at least 30 minutes and up to 2 hours (turning the bag occasionally to re-distribute the marinade).
Prepare the SALAD:
Cut a piece off one end of the corn so that you can stand it flat inside a bowl. Use a sharp knife to cut down the side of the cob and gather the corn kernels into the bowl. Set aside.
Heat 2 teaspoons olive oil in a medium skillet over medium heat. Add the corn, green onions, tomatoes and rosemary. Cook, stirring, 3 to 4 minutes, just until the corn begins to soften and the tomatoes begin to wilt.
Spoon the corn/tomato mixture back into the bowl. Add the vinegar, salt and pepper. Let stand at room temperature.
GRILLING AND FINISHING:
Spray a grill rack with nonstick spray. Preheat the grill to medium high.
Remove steak from marinade (discard marinade). Place the steak on the grill rack and grill until an instant read thermometer inserted in the side of the steak registers 145℉. for medium, 3 to 4 minutes on each side.
Transfer the steak to a cutting board and loosely cover with foil; let stand 2 to 3 minutes. Cut across the grain thinly into 12 slices. Top each serving with corn/tomato salad.
Notes
Optional: Add 1 large peeled and chopped cucumber to the corn salad.