Preheat oven to 350℉ and line a large sheet pan with parchment paper. Set aside.
In a small bowl, whisk together avocado oil, Worcestershire sauce, and seasonings until well-combined. Set aside.
Place sirloin in center of sheet pan and disperse veggies around sirloin, in an even layer.
Pour over sauce mixture, then gently toss veggies and coat sirloin all over in sauce.
Place on middle rack of oven and let cook ~15 minutes.
Then, turn broiler on and place on upper rack — let broil ~5 minutes or until veggies and sirloin have browned. Let meat rest ~3 minutes, then slice into thin strips.
Next, place cheese slices over top and return to broiler for ~5 minutes or until cheese has melted. Garnish with fresh parsley.