Preheat an oven to 350 degrees F (175 degrees C). Fill a large pot with lightly salted water and bring to a rolling boil over high heat. Once the water is boiling, stir in the egg noodles and return to a boil. Cook the pasta uncovered, stirring occasionally, until the pasta has cooked through, but is still firm to the bite, about 5 minutes. Drain well in a colander set in the sink.
While the pasta is cooking, stir the tuna, condensed soup, peas with mushrooms and onions, onion, milk, salt, and pepper in a bowl until evenly mixed. Gently stir in the cooked pasta, then pour the mixture into a 9x13 inch baking dish. Sprinkle evenly with dry bread crumbs.
Bake in the preheated oven until the casserole is bubbling and the bread crumbs are golden brown, about 20 minutes.