A few things. First, I wouldn't use grape seed oil. It is too astringent. I always use sunflower oil or melted butter (melted butter is what the restaurants use). Sometimes I use olive oil, but I wouldn't recommend it - yes it is healthier, but high heat will put some flavors a little off. Next, change your spices. The best steaks let the flavor of the meat come through. Montreal steak mix reminds me of a beef stew. I use a cajun blackening seasoning (not much at all - it is mainly there for the smokiness), then I use alderwood smoked sea salt. I have also had good luck with hawaiian black sea salt and oak smoked sea salt. I personally like the hawaiian black sea salt the best, but guests seem to like the alderwood a bit more. Use fresh ground black pepper - I have tellicherry. Your steaks should be cool when you add the oil and seasonings - Not ice cold. I rub the oil on one side, then add the seasonings. Flip, then add the oil to the other side then season again. Let them sit in the seasonings for at least 30 mins at room temp (make sure no dogs can get to them - I've made that mistake before...) When you grill this steak, you want to sear then flip. After the other side is seared again, turn the temp down and cook slower than you currently are. You already preserved most of the goodness within the steak, but it will get chewy if you cook too fast. Let the steaks rest for 3 min before plating. Cooking steaks is all in the technique - not the seasonings.
Ok that was level 2. Level 3 is this - get yourself an immersion cooker. This method will take a few hours longer than the normal method, but even a crappy piece of meat will be more tender than filet using conventional methods. Lightly season the steaks with the same seasonings. If you like the "montreal steak" flavor - go ahead and add a little raw onion and garlic to the bags. Sous vide your steaks to the recommended times/temp based on how you want it cooked. I always do a little less time so that I can get a little more grill time (and good looking grill marks). When the sous vide is complete, drain the bags and set the steaks on a cutting board. (alternately save the juice for some of the best au jus ever) Oil them and add the same seasonings like you would normally. Your grill should be on med-high to high at this point. Sear both sides like you normally would. After both sides are seared you are done. Rest like you normally would. I cooked 7 whole filets for a wedding like this. Never got so many compliments.
One thing I forgot to mention - oil your grill when heated (throw some oil on your grill scraper). It will season and clean your grill and provide a better chance of getting really nice looking grill marks.