In medium bowl, combine all ingredients except bread and margarine; mix well.
To assemble sandwiches, spread 1/2 cup of tuna mixture on each of 5 slices of bread.
Cover with remaining bread slices.
Spread margarine on outside of each sandwich.
Heat large skillet over medium-high heat or heat griddle to 375°F.
Add sandwiches; cook 1 to 2 minutes on each side or until bread browns and sandwiches are hot.