Cut the chicken into chunks about 1-1 1/2 inches, large enough that they won't fall off of the skewers
In a small mixing bowl, whisk beer, ranch powder, olive oil, and garlic
Pour about 2/3 of the marinade over the chicken, cover, and refrigerate for at least 2 hours (save the remaining 1/3 marinade in the refrigerator for later)
Parboil the Potatoes
About 30 minutes before grilling, cover the potatoes with water in a large stockpot and bring to a boil
Turn off the heat and cook for about 5 minutes, until the outside starts to soften but the centers are still hard
Drain the potatoes and immediately run under cold water to stop the cooking process
Prepare Skewers
If you are using bamboo skewers, soak for 20-30 minutes before preparing
Heat the grill to a medium heat
Alternate adding chicken and potatoes to the skewers until it's all been used
Brush reserved marinade over the skewers
Grill the kabobs for about 20-25 minutes (depending on the temperature of the griluntil the chicken is cooked through and potatoes are crispy