For the beef tenderloin-pumpkin skewers, rinse the beef tenderloin in cold water and pat dry. Cut into approx. 3 x 3 cm cubes. Cut the pumpkin flesh into cubes.
For the marinade, pluck the rosemary needles from the stems and chop finely. Mix with olive oil, salt and coarsely ground pepper in a large bowl to make a marinade. Allow the meat and squash cubes to marinade briefly.
Thread the meat cubes, squash cubes and rolled-up prosciutto slices alternately onto the skewers. Grill the beef tenderloin-pumpkin skewers on the grill grate on all sides. The meat may still be a little pink inside.