I am looking through the list of ingredients of a Balance bar which I bought recently from the supermarket, Chocolate flavor. There are no gluten-containing ingredients on the label.
However, there is note regarding "Allergy Information" that says the food processing equipment used to make the Balance Original bars are also used to process foods with peanuts, tree nut, egg, wheat and sesame seeds.
Therefore, I guess it may depend on your level of gluten sensitivity. If you must avoid any and all molecules of wheat, because of coeliac disease, non-coeliac gluten intolerance, and dermatitis herpetiformis, then you're better off without this brand of diet bar.
I checked the Almond Brownie and Yogurt Honey Peanut flavors, and they're basically the same, except obviously they contain the nuts advertising in their variety.
Their Balance Bare line of bars obviously contain a lot of nuts, so anybody who needs to avoid peanuts must pass on those. And there is a Cinnamon Oats & Honey flavor. Some believe that it's all right to eat oats, because they don't contain gluten. However, others find they're better off avoiding oats also, because they're often contaminated with gluten, and a substance in them closely resembles gluten.

The Balance Gold line seem to be the same as the Original.
The Balance Pure line is advertised as "Gluten Free." This includes Cherry Pecan, Berry Berry Chia and Chocolate Cashew. They contain only evaporated cane juice, cashews, soynuts, dates, cocoa, soy protein isolate, cherries, fig paste, almonds, peanut oil and salt.
They note that they're processed with machines that also processes milk, egg, peanut, sunflower seed, sesame seed and other tree nuts -- but NOT gluten!
However, I must point out that these bars contain a lot more carbohydrate calories than the Zone range of 40/30/30 nutrition recommended by Dr. Barry Sears. They are manufactured by the Balance company, but they are NOT balanced according to the Zone formula -- and that's true of all these Balance bars except the Balance Original line. They are the only ones with labels claiming to be 40% carbohydrates, 30% protein and 30% fat -- because they're the only Balance meal replacement bars that actually meet the Zone specifications.
I will admit, however, that the Balance CarbWell line of Chocolate Peanut Butter and Caramel N Chocolate contain only two grams of carbohydrates, so they're actually out of the Zone in the opposite direction. If you can't eat a Balance Original bar, a CarbWell bar will at least make sure your insulin won't spike up too high. And you won't get overloaded with protein unless you continue to eat too few carbs for a few days. They actually have a lot of carbs, but most of it comes from calorie-free sugar alcohol.
They make no claim to being gluten free, although they don't contain any gluten ingredients, so they must be manufactured on the same food processing equipment.
So deciding whether Balance bars are gluten free is not simple and easy, but not hard either.
Next: Balance Bars - Nutritional Info -- about their health benefits.