Combine first 4 ingredients in a blender or food processor, and process until blended, stopping once to scrape down sides.
Cover and chill 8 to 24 hours.
Sprinkle steaks with salt and pepper.
Grill steaks, covered with grill lid, over medium-high heat (350° to 400°) about 8 minutes on each side or until fish flakes easily when tested with a fork.