If your deer cube steak is not already tenderized, gently pound it with a meat mallet to ensure even thickness and tenderness. Season both sides generously with salt, pepper, garlic powder, and onion powder.
Place the flour in a shallow dish. Dredge each piece of deer cube steak in the flour, ensuring it's fully coated. Shake off any excess flour.
Heat vegetable oil in a large skillet over medium-high heat. Once the oil is hot, carefully place the floured deer cube steaks in the skillet, ensuring not to overcrowd the pan (cook in batches if necessary). Sear for about 2-3 minutes per side, until nicely browned.
Remove the deer cube steak from the skillet and set aside. In the same skillet, reduce the heat to medium. Pour in the beef broth, milk, and Worcestershire sauce. Whisk to combine, scraping up any browned bits from the bottom of the pan (this adds flavor to the gravy).
Bring the gravy to a simmer and cook for about 5-7 minutes, or until it slightly thickens. You can add a cornstarch slurry (1 tbsp cornstarch mixed with 2 tbsp cold water) if you prefer a thicker gravy. Stir in the slurry gradually until desired consistency is reached.
Return the seared deer cube steaks to the skillet with the gravy. Reduce heat to low, cover, and simmer for another 10-15 minutes, or until the deer cube steak is tender and cooked through. Ensure the internal temperature reaches 160°F (71°C) for safe consumption.
Serve hot over mashed potatoes, rice, or your favorite side dishes. Spoon the delicious gravy generously over the deer cube steak.