Use a marinade and keep the steak cool.  I use either a soy sauce or red wine based marinade with olive oil, either fresh or dried onions and/or garlic, a few herbs and a dollop of maple syrup.  Flank steak works particularly well.  Grill it five minutes a side over hot coals or a fire for rare, and slice it thin diagonally (top to bottom) across the grain.  I pack the steak in a plastic bag with the marinade and no air, refrigerate it before leaving home, and keep it with the cool but not frozen stuff in the food pack (cheese, sausage, butter, etc.)  I usually use it about 3 days out, after frozen birds, but before smoked mammals.