Bring a large pot of salted water to a boil and cook the tortellini according to package directions, then drain and set aside.
Heat olive oil in a large skillet over medium-high heat.
Add the diced onions and bell peppers to the skillet and sauté until softened and slightly caramelized, approximately 5-7 minutes.
Add the lean ground beef to the skillet, season with salt, pepper, and garlic powder, and cook until fully browned. Drain any rendered fat.
Lower the heat to low. Whisk together the skim milk and Greek yogurt in a small bowl before stirring into the beef and vegetable mixture.
Gradually stir in the shredded provolone cheese until the sauce is smooth and melted.
Add the cooked tortellini to the skillet and toss gently until every piece is coated in the provolone sauce.
Serve immediately while hot.