Preheat the oven to 400°F. Grease a 9-inch pie plate.
Heat a large skillet over medium-high heat. Add the ground beef and diced onion, cooking until the beef is browned and the onion is softened. Drain any excess grease.
Stir in the taco seasoning until the beef mixture is evenly coated.
Spread the seasoned beef mixture evenly across the bottom of the prepared pie plate.
Sprinkle the shredded cheddar cheese over the beef.
In a medium bowl, whisk together the baking mix, milk, and eggs until smooth.
Pour the mixture evenly over the beef and cheese in the pie plate.
Bake for 25–30 minutes, until the top is golden and a knife inserted into the center comes out clean.
Let the taco pie rest for 5–10 minutes before slicing. Serve warm with your favorite taco toppings.
