How to Make It
Mix first 4 ingredients in a medium bowl until well combined. Season with salt and pepper. Place 1/2 tuna salad in an airtight container. Cover and chill (will keep in fridge for up to a week). Fold peppers and olives into remaining salad.
In a separate medium bowl, drizzle oil and vinegar over lettuce; toss well. Season with salt and pepper and toss again. Place tuna salad over lettuce; serve with crackers, if desired.