In a small bowl, mash together softened butter, minced garlic, and oregano until well combined. Set aside at room temperature.

Place ribeye in the freezer for 15 minutes to firm up - this makes it much easier to slice paper-thin. Slice against the grain into strips no thicker than 1/8 inch.

Heat oil in a large skillet over high heat until just smoking. Add half the beef in a single layer, season with salt and pepper, and let it sear undisturbed for 90 seconds until browned. Toss quickly, cook 30 seconds more, then transfer to a plate. Repeat with remaining beef.

Reduce heat to medium. Add onion and pepper to the same skillet with a pinch of salt. Cook 6-8 minutes, stirring occasionally, until softened and caramelized at the edges. Return beef to pan, add Worcestershire, toss everything together, and remove from heat.

Preheat oven to 425F. Spread garlic butter evenly over both bread halves, working it into all the crevices. Place on a baking sheet and bake 8 minutes until edges are lightly toasted.

Remove from oven. Distribute half the provolone across both halves, then pile the hot beef and vegetable mixture on top. Cover with remaining cheese. Return to oven for 5-7 minutes until cheese is fully melted and bubbling with light brown spots. Switch to broil for 1-2 minutes if you want more color - watch closely.

Let rest 2 minutes, then slice into thick pieces with a serrated knife. Serve immediately while the cheese is still stretchy.