Allow piecrust to stand according to package directions. Preheat oven to 375 degrees F. Line a large baking sheet with parchment paper. Place piecrust on the prepared baking sheet; roll into an 11-inch circle. Set aside.
For filling, in a medium skillet, cook leek and fennel in hot oil over medium heat for 5 to 6 minutes or until tender, stirring occasionally. Remove from heat. Stir in cheese, olives, and thyme. Cool slightly.
Spread filling in center of pastry, leaving the outer 1 1/2 inches uncovered. Fold uncovered pastry up over filling.
Bake for 30 to 35 minutes or until pastry is golden brown. Cut into wedges and serve warm.