You can substitute literally any spices for this. Porcini powder is a good one, and so would French quatre epices. Hell, even lemon pepper or that standard Italian seasoning you see in stores would work. Experiment. One thing: Please use whole doves here, not breasts. Doves and pigeons are so easy to pluck it is a crime not to serve them whole.
Coat the doves in the oil, then toss in a bag or plastic container with the spice rub. Let the birds sit in the fridge for at least an hour, and up to a day.
When you are ready to cook them, get the grill hot, but leave a cooler spot where there are no coals underneath, or, if you have a gas grill, turn off one burner. Make sure the grates are clean, and right before you put the doves on the grill, wipe down the grill with a paper towel soaked in vegetable oil. Use tongs to do this.
Put the doves or squab, breast side up, on that cool side of the grill for 5 minutes with the grill cover down.
Move the doves to one side -- you're searing the wings and legs here -- and grill over the hot side of the grill (with the cover up) for 2 minutes, or until the side is nice and browned. Repeat on the other side.
Finally, flip the doves so the breast is facing the flame and grill for another 1-2 minutes, or until the breast is nicely browned, with a little char on it. Let the doves rest for 5 minutes before eating.