Wash the meat, dab dry, cut into cubes of about 5 cm and place in a bowl. For the marinade mix mustard, beer, honey and thyme. Season vigorously with salt and pepper. Pour the marinade over the meat and mix well. Cover and chill for about 1 hour.
In the meantime peel the onions, cut into eighths. Put the meat cubes and onions alternately on the skewers, put marinade aside. Grill the meat skewers on the hot grill for 15-20 minutes while turning. Spread the rest of the marinade over and over again.
Wash the peppers, dab dry and after 5-10 minutes grill with them, turning occasionally.