Whisk canola oil, onion, lemon juice, Worcestershire sauce, soy sauce, garlic powder, and pepper in a bowl until marinade is well mixed. Place elk steak in a large resealable plastic bag and pour marinade over meat. Coat meat with marinade, squeeze out excess air, and seal bag. Marinate in the refrigerator for at least 4 hours, turning occasionally.

Preheat grill for medium heat and lightly oil the grate. Drain elk steak and discard marinade.

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