In a large bowl, mix together the red wine, olive oil, honey, mustard, steak spice, and Greek oregano. Add your pork fillets to the bowl and coat evenly with the marinade. Alternatively, pour the marinade into a large re-sealable plastic bag (like a freezer bag) and then add the pork fillets. Ensure that they are coated thoroughly. Marinate in the refrigerator for at least 12 hours. You should occasionally mix the pork around so that the marinade is easily distributed.
1/4 cup red wine, 1/4 cup olive oil or vegetable oil, 1/2 tbsp honey, 1/2 tbsp yellow mustard, 1/2 tbsp Montreal steak spice, or another type of steak spice, 1/2 tbsp dry Greek oregano, 5 pork fillets from a pork tenderloin, each fillet cut into 1 ½ inch thick slices