Preheat oven to 425°. Drain beef, reserving 1/4 cup juices; shred meat with 2 forks. In a large skillet, heat oil over medium-high heat. Add onion and pepper; cook and stir until tender, 1-2 minutes. Add garlic; cook 30 seconds longer. Remove from heat; stir in beef and reserved juices., Unroll 1 pie crust; cut in half. Layer 1/4 cup shredded cheese and about 1/3 cup beef mixture over each crust half to within 1/2 in. of edge. Fold crusts over filling; press edges with a fork to seal. Place on a greased baking sheet. Repeat with remaining crust and filling., Bake until golden brown, 15-18 minutes. If desired, serve with queso dip.