Cut ribeye steak into 16 uniform pieces and par-boil halved baby Yukon Gold potatoes for 5-7 minutes until slightly tender.

In a bowl, whisk together soy sauce, ketchup, vegetable oil, white vinegar, brown sugar, and garlic powder until well-blended.

Marinate steak pieces and mushrooms in a resealable bag with the prepared marinade for at least 1 hour.

Assemble skewers by threading marinated steak, potato halves, and mushrooms alternately.

Preheat grill to medium-high heat and grill kabobs for 3-4 minutes per side until steak is medium-rare.

Baste kabobs with leftover marinade during the last few minutes of grilling, then let them rest before serving.