Cook Arborio rice according to package and set aside to cool.
Preheat oven to 400°F. Coat sides and bottom of 9x13 baking dish with non-stick cooking spray.
Heat olive oil in skillet over medium-high heat. Add ground beef, sauteing and breaking up the meat for 3 minutes. Add in minced onion, garlic, and salt & pepper, mixing well. Stir in peas. Add in 1 cup of sauce, combining and cooking until meat is browned. Remove from heat.
In large mixing bowl, combine rice with 2 beaten eggs, half the pecorino cheese, and 2 cups of sauce.
Pour half the rice mixture into the greased baking pan, spreading rice from edge to edge. Add meat mixture on top of the rice, and spread evenly. Sprinkle half mozzarella over meat mix. Cover with remaining rice mixture, evenly spreading from edge to edge. Bake for 20 minutes.
Carefully remove from oven and sprinkle with the remaining pecorino and mozzarella cheese. Continue to bake an additional 10 minutes or until cheese starts to turn golden.
Cut into squares and serve with additional sauce over top of individual pieces, if desired.