If "grope" means to search blindly or clumsily:
* Find
* Discover
* Locate
* Identify
* See (if the context implies a lack of sight)
* Understand (if the context implies a lack of clarity)
If "grope" means to touch someone inappropriately:
* Respect
* Honor
* Admire
* Appreciate
* Treat with dignity
If "grope" means to feel around for something:
* Reach
* Grasp
* Hold
* Take
The best antonym will depend on the specific context and the meaning you are trying to convey.