As others have pointed out, you will not make venison taste like beef. It's not beef, and because of the different in type of fat and fat content, will never taste the same.

An excellent marinade for good cuts of meat destined for the grill (i.e. backstrap, tenderloin) is one you've probably used before, but I'll say it anyway: black pepper, worsheschire, and italian dressing.

I use about a cup of dressing to 1/3 cup of worsheschire, and liberally sprinkler the meat first with pepper. I let it all sit in a bowl for at least six hours before cooking medium rare on the grill. Really excellent, as well as cheap and easy.

Hope this helps.

MOCraig