Serve tonight: Preheat grill to medium. In large bowl, combine first 4 ingredients. Form into 6 oval patties. Drizzle oil on onion.
Place patties and onions on grill. Grill, turning once, until internal temperature of burgers reaches 165°, about 10-12 minutes, and onions reach desired doneness. Salt and pepper to taste. Top burgers with Swiss cheese and divide onions evenly over burgers. Serve on slices of grilled marble rye bread. Makes 6 servings.
Serve with fresh vegetable sticks and dip. For a great dip, try preparing our Dill Pickle Dip Mix as directed on the package.
Freeze for later: Combine first 4 ingredients. Form into 6 oval patties and place between waxed paper in a gallon resealable freezer bag. Seal well, label and freeze. Thaw completely. Grill as directed above.
Tip: Form into round patties and serve on hamburger buns.