Cook meat in a medium nonstick skillet over medium-high heat until browned, stirring until it crumbles. Drain, if necessary and return to skillet. Add tomato sauce, and cook until heated.
While meat cooks, coat a 13- x 9- x 2-inch baking dish with cooking spray. Unroll pizza crust dough, and press into bottom and halfway up sides of baking dish. Line bottom of pizza crust with 3 slices mozzarella cheese. Top with meat mixture.
Bake, uncovered, at 425° for 12 minutes. Top with remaining 3 cheese slices, and bake 5 additional minutes or until crust is browned and cheese melts. Cool 5 minutes before serving.