This one-pot meal is quick, easy, and delicious.
In a large pot of boiling salted water, cook orzo according to package instructions. In last 2 minutes of cooking, add asparagus and corn. Drain and rinse under cold water to stop the cooking. In pot, whisk together vinegar, olive oil, and mustard. Add orzo mixture, tomatoes, and tuna, and toss to coat; season with salt and pepper and top with oregano.