Chop the cucumber, cherry tomatoes and bell pepper. Add them to a large bowl together with the salad mix. Drain the tuna, divide it into bite-sized chunks, and add it to the salad. Drizzle the olive oil and lemon juice, and season with salt and pepper. Mix well.
Divide the salad into individual bowls and add the hard boiled egg cut in quarters.
Notes
You can replace the salad mix with romaine lettuce or iceberg lettuce if you wish.