It is possible to cook on a grill under a covered porch, but it is important to take precautions. The first thing to consider is the type of grill you are using. If you are using a charcoal grill, you will need to be sure that there is proper ventilation so that the smoke can escape. You will also need to be careful of any sparks that may come from the grill. If you are using a gas grill, be sure that the area is well-ventilated so that any fumes can disperse quickly. Another thing to keep in mind is the heat of the grill. You will want to make sure that the area around the grill is clear of any flammable materials. If possible, set up the grill on a non-flammable surface such as concrete or bricks. Be sure to keep a close eye on the fire and never leave it unattended. With proper precautions, cooking on a grill under a covered porch can be safe and enjoyable.