1/4 cup red wine vinegar
2 tablespoons vegetable oil -- usually use canola
2 tablespoons soy sauce -- can use low sodium
2 tablespoons ketchup
1/4 teaspoon onion powder -- don't usually measure
garlic powder -- to taste
pepper -- to taste

Gail's Notes: Here is a recipe for a marinade that I use. I love this one, have used it mostly for chicken but I think you can use it for meats, venison, deer meat, etc. I don't think I've ever given it out, so you should feel privileged! When I marinate with this and cook on the grill, I've always gotten compliments on the meat. I think you could do the same on the forman grill, I just usually don't get started early enough to marinate it long enough.