Place the tenderloin on a large cutting board and pat dry with a paper towel. Using a sharp knife, remove the “wing” muscle from the fatter end of the loin. Cut this into steaks and reserve for later use.
Carefully butterfly the tenderloin and flatten it to an even thickness.
Sprinkle the breadcrumbs, lemon zest, and oregano over the surface of the beef. Sprinkle with the cheese and arrange the prosciutto in an even layer on top.
Carefully roll the tenderloin up, forming it into a roulade. Tie or truss the roulade tightly using butcher’s twine.
Brush all sides of the roulade with the blended oil and season with salt and pepper or the steak seasoning blend.
Grilling
Let the tenderloin come to room temperature before cooking.
To reverse sear: cook the tenderloin on a preheated 200 degrees F (95 degrees C) grill and cook to an internal temperature of 110 degrees F (45 degrees C). Finish the roulade on a 600 degrees F (315 degrees C) grill and brown the crust nicely, bringing the tenderloin to a final internal temperature of 125 degrees F (50 degrees C).
To sear first: cook the tenderloin on a preheated 500 degrees F (260 degrees C) grill. Turn the meat every 5 minutes to get an even sear. Remove from the heat when the internal temperature reaches 125 degrees F (50 degrees C).
Portabella Red Wine Sauce
Place the oil in a small saucepan over medium-high heat. Add the garlic and let brown slightly. Add the shallots and cook, stirring occasionally, until translucent.
Add the portabellas and cook for 3 minutes, then add the wine and rosemary. Reduce the heat to low and let the wine reduce by 2/3.
Add the beef stock and continue to cook until the sauce is reduced by half. Remove the rosemary sprig and season with salt and pepper.
To Serve
Place the roulade on a large cutting board and remove the butcher’s twine. Slice the roulade into 1-inch-thick pieces and serve with the red wine portabella sauce.