Pre-heat the grill to medium-high.
In a one gallon plastic bag or a high-sided baking dish, whisk together the orange, lemon and lime juice and zest, thyme leaves, grainy mustard and EVOO. Place the meat or fish into the marinade and let sit for at least 15 minutes. If using all the meats and fish, place into separate containers, making sure the different types of meat aren’t touching. For easier cleanup and storage, use the plastic bag rather than the baking dish.
When your grill is ready, take the meat and/or fish out of the marinade and discard the rest. Place on the grill and cook until desired doneness: Halibut – 3 minutes on each side; pork chops – 5 minutes per side; chicken breast, thighs and legs – 4-5 minutes per side; flank steak – 4 minutes per side) Take the meat off the heat and let rest for about 3-5 minutes, then serve.