Place the antelope cutlets between two sheets of parchment paper on a firm, level surface. Using the smooth side of a meat mallet, pound the steaks to about ¼-inch thickness.
In a shallow dish, combine the flour, garlic powder, onion powder, and salt. Dredge each cutlet in the flour mixture, shaking off any excess.
Heat 2 tablespoons of butter and the olive oil in a large skillet over medium-high heat. Add the floured cutlets and cook until lightly browned, about 1½ minutes per side. Remove the steaks from the skillet and set aside.
Melt the remaining butter in a separate skillet. Add the mushrooms, onions, and garlic, cooking until the mushrooms are golden and tender, about 8–10 minutes.
Pour in the Marsala wine, stirring to loosen any browned bits from the pan. Return the antelope cutlets to the skillet and simmer gently until tender and heated through, about 5 minutes.
Serve the antelope Marsala over steamed basmati rice with a crisp green salad on the side.