Coat grill rack with non stick cooking spary. Preheat grill to high direct heat (400 degrees). Meanwhile, combine oil and lime juice in small bowl. Combine brown sugar, chili powder, paprika and garlic powder in another small bowl. Brush corn with lime juice mixture, then coat with chili powder mixture, reserving remaining lime juice mixture.
Rub both sides of steaks with remaining chili powder mixture. Place steaks and corn on grill. Grill, uncovered, to desired doneness, turning once halfway through cooking (11 to 16 minutes for rare to medium steaks, 11 minutes for corn). Remove from grill; cover steaks to keep warm.
For corn relish, cut grilled corn from cobs and place in medium bowl. Add reserved lime juice mixture, tomatoes, onion and parsley; toss. Season with salt to taste. Serve with steaks.