I started making keto grilled asparagus in foil packets years ago because I was tired of spears falling through the grill grates. The foil solves that completely. You get tender, evenly cooked asparagus without losing a single spear to the coals, and cleanup is just crumpling up the foil and tossing it.
The method is simple. Toss a pound of asparagus with olive oil, salt, pepper, and a squeeze of fresh lemon, then seal it all in a foil packet with some room at the top. That air space matters. It lets the steam circulate so the spears cook evenly instead of getting mushy on the bottom and raw on top. I grill mine over direct heat for 5-8 minutes, and here is my favorite part: in the last minute, I open the packet and let the spears sit directly on the grate. You get those charred grill marks on asparagus that was already perfectly cooked inside the foil. Best of both worlds.
One thing I have learned after years of grilling this way: olive oil is the right fat here, not butter. Butter burns fast at grill temperatures, and it really falls apart once you open that foil for direct contact. Olive oil has a higher smoke point and holds up through the whole process. I finish with freshly grated parmesan after it comes off the grill, and that is where the richness comes in without the scorching risk. This low carb side dish pairs with just about anything off the grill. I serve it next to my grilled marinated chicken almost every weekend in the summer.
If you are working with thick asparagus spears (thicker than a pencil), give them an extra 2-3 minutes in the packet. Thin spears cook faster and can go limp if you leave them too long, so check at the 5-minute mark. I have made this with both, and honestly I prefer the thicker stalks for grilling because they hold up to the heat and have a meatier bite.
This works on a campfire too. I have made these packets on camping trips by setting them right on the grate over embers. Same timing, same result. And if the weather turns on you, the oven at 350 degrees is a solid backup. The closed oven environment traps moisture the same way the foil does, so the spears come out just as tender. They will not get grill marks, but the lemon-parmesan finish still makes them worth it.
For more asparagus options, I have an oven roasted asparagus recipe that is great for weeknights, and my air fryer asparagus gets crispy edges in under 10 minutes. If you want something more substantial, try my bacon wrapped asparagus kebabs on the grill. And if you are building a full cookout spread, my Traeger grilled vegetables, grilled pizza, and homemade keto BBQ sauce round things out nicely.