In a saucepan, simmer the first four ingredients until reduced to 1 cup. Put tenderloin slices into a bag and pour marinade over. Marinate overnight.
On a barbecue at Medium/high heat, grill the tenderloins until done - about 6-7 minutes per side. Check for done-ness, you don't want to overcook, but you want them to be cooked through and still juicy. This is lovely served with homemade applesauce and coconut rice. Serve with Mettler Epicenter Zinfandel.