Heat the olive oil in a skillet over medium-high heat. Sprinkle the chicken with salt and pepper and cook until golden brown, about 3 minutes on each side. Set aside on a plate to cool.
In a medium bowl, add the olives, onions, capers and garlic. Chop the cooled chicken and add it to the bowl. Add the feta cheese and lemon juice and toss all the ingredients together.
To serve, slice the baguettes and pile some of the mixture on each baguette.