Cook the Pasta: Boil water in a large pot and cook the pasta according to package instructions. Once al dente, drain and rinse under cold water to stop the cooking process.
Prep the Veggies: While the pasta cooks, chop up the cucumbers, green onions, and bell peppers. Drain the sweet corn if using canned corn.
Mix Ingredients: In a big mixing bowl, combine the cooked pasta, drained tuna, sweet corn, diced cucumbers, chopped green onions, and diced bell peppers.
Make the Dressing: In a separate small bowl, whisk together olive oil, lemon juice, salt, and pepper.
Combine Everything: Pour the dressing over the pasta mixture and toss until everything is well coated.
Chill and Serve: Allow the salad to chill in the refrigerator for at least 15 minutes before serving.