Whisk olive oil, lime juice, jalapeno pepper, garlic, salt, and pepper together in a flat baking dish. Place the tuna steaks in the dish, turning to coat entirely in marinade; cover the dish with plastic wrap and refrigerate for 20 minutes.
Preheat an outdoor grill for high heat and lightly oil the grate.
Cook steaks on the preheated grill until beginning to firm and hot in the center, 5 to 7 minutes per side.
