Whisk together canola oil, onion, lemon juice, Worcestershire sauce, soy sauce, garlic powder, and pepper in a small bowl until combined.

Place elk steak in a large resealable plastic bag and pour in Worcestershire mixture. Coat steak with marinade, squeeze out excess air, and seal the bag. Marinate in the refrigerator for at least 4 hours, turning occasionally.

Preheat the grill for medium heat and lightly oil the grate.

Drain steak and discard marinade.

Cook steaks on the preheated grill until they begin to firm up and are hot and slightly pink in the center, about 5 minutes per side. An instant-read thermometer inserted into the center should read at least 140 degrees F (60 degrees C).