To be sure, you MUST:
* Check the bolt pattern: This is usually a 5x120.5 or 6x139.7 (depending on the year). Both the Tahoe and Envoy *might* have either, but it's not guaranteed to be the same for both. You need to find the bolt pattern for *both* your specific Envoy and the Tahoe's rims.
* Compare wheel diameter and width: The diameter must fit within your Envoy's wheel well and not rub against suspension components or the body. The width needs to be compatible with your Envoy's tire size.
* Consider the offset: Wheel offset affects how far the wheel sits in or out from the hub. An incompatible offset can lead to rubbing.
Unless the bolt pattern, diameter, width and offset are *exactly* the same, the Tahoe rims will likely not fit on your GMC Envoy, or at least not safely. It's best to check your owner's manual or a reputable online resource like Tire Rack to find the specifications for your Envoy's wheels. Then, you'll need to get the specs for the Tahoe rims in question. Only then can you be certain they're compatible.