Preheat oven to 400°F. Preheat a medium cast-iron skillet over medium-high.
Add beef and cook, stirring often to crumble, until browned and no longer pink, about 6 minutes. Drain fat and return beef to skillet.
Stir in Greek seasoning, thyme, and 1 teaspoon of the garlic powder; cook, stirring constantly, until beef is coated and fragrant, about 1 minute.
Stir in onion soup and beef consommé, and whisk until smooth. Cook until reduced and thickened, about 5 minutes.
Stir in mixed vegetables and remove from heat.
Whisk together flour, sugar, and remaining 1 teaspoon garlic powder in a large bowl until no lumps remain.
Add cold butter; use a pastry cutter to cut butter into flour mixture until fully coated and butter is the size of peas.
Gradually add buttermilk; stir until just combined. (Batter should be wet but hold some structure.)
Scoop 8 (3-tablespoon) biscuits onto beef mixture, spacing 1 to 2 inches apart. Sprinkle biscuits with cheese.
Bake in preheated oven until bubbly and biscuits are golden brown, about 20 minutes. Let sit at least 5 minutes before serving.
