Make the chimichurri first by combining the parsley, oregano, garlic, red pepper, and vinegars in a mortar and pestle. Work this mixture into a thick paste and add a heavy pinch of kosher salt and oil and combine until you have a thick but chunky sauce. A small food processor works for this too — just combine the ingredients with a few short pulses.
Heat a grill for two zone cooking with one side set to high. Preheat two small cast iron skillet over high heat and the move to the indirect side to keep warm. Make sure the cheese steaks are cold and put them over direct high heat to brown for just 2 minutes. Flip these cheese steaks into the hot cast iron skillets. Cook covered until the cheese is melted and bubbly about 2 to 3 minutes more. Meanwhile brush the baguette slices with olive oil and grill until charred, about 1 minute per side.
Serve the hot cheese with a big dollop of chimichurri and baguette for dipping.