Good question ekgrows. I hope some of the pros chime in on this as it sure sounds like a tasty addition.

I honestly don't know of any reason why the char should affect anything. No difference than say roasting and then canning peppers.

The only concern I can think of is the effect on the corn of the double-processing, or rather the cooking followed by the long processing if you can the relish. Mushy or chewy corn maybe?

Make up a small batch for fresh eating first and see if you like it, if it is worth canning.

Dave

I can't think of any reason not to can it either.

Just as an FYI, here's a recipe for a Southwestern Corn Relish that was posted here a while back (this is a clip from a post by Annie - yes, THAT Annie of salsa fame - the original recipe came from Carol aka readinglady) that sounds perfect for grilled corn:

Annie's Comments:
Carol (Readinglady) gave me a recipe for Southwestern Corn Relish and I canned 16 pints of it, my daughter loves the stuff. I mix a jar of it with a jar of my salsa and a can of drained black beans and it makes an awesome salsa, but it is more vinegary than it is sweet.

Southwest Corn Relish
Tuesday, October 11, 2005
The Oregonian
Makes 6 to 7 pints

This condiment is a delightfully corny blend of tang and heat. The jalapeno chiles are tiny islands of spicy flavor that can be avoided by folks with more sensitive palates because they are relatively large in size. The relish is great to have on hand to top a platter of nachos or other Southwest-flavored dishes, or to scatter over green salads. It's also wonderful stirred into rice, along with a bit of cheese and a dollop of sour cream.

• 20 ears sweet corn (to yield 2 1/2 quarts -- 10 cups -- of corn kernels)
• 2 cups chopped yellow onion
• 1 cup chopped green bell pepper
• 1 cup chopped red bell pepper
• 1 cup seeded and chopped Anaheim chiles
• 3 jalapeno chiles, stems removed and sliced into very slender rings
• 1 cup chopped celery
• 4 cups cider vinegar
• 11/2 cups water
• 3/4 cup granulated sugar
• 1 tablespoon salt
• 2 tablespoons yellow mustard seeds
• 1 tablespoon whole cumin seeds
• 2 teaspoons celery seeds

If you plan to store the corn relish in jars at room temperature, wash 7 pint canning jars; keep hot until needed. Prepare lids as manufacturer directs. If you want to store it in the refrigerator, follow the directions below.

Cut kernels from enough ears of corn to measure 2 1/2 quarts of kernels. Add the corn to a large, heavy-bottomed pot, along with the onion, bell peppers, chiles, celery, vinegar, water, sugar and salt. Make a spice pouch for the mustard seeds, cumin seeds and celery seeds with several layers of cheesecloth or a clean square of cotton fabric (from a clean T-shirt or a handkerchief, for example) tied with string. Add the pouch of spices to the pot and stir to mix up the ingredients. Bring to a boil and simmer, uncovered, stirring occasionally, until the mixture is slightly thickened but there is still plenty of vinegar solution remaining, about 20 to 30 minutes. Retrieve the spice pouch and, before removing it, press it firmly against the side of the pot with the back of your spoon to extract as much flavor as possible.

To store in the refrigerator: Place the hot relish in plastic freezer containers or glass jars, cover with tightfitting lids and refrigerate for 6 months or longer (quality may suffer after that, but the relish will be safe to eat). For long-term storage at room temperature: Ladle the hot relish into 1 hot jar at a time, leaving 1/2-inch head space. Wipe jar rim with a clean, damp cloth. Attach lid. Fill and close remaining jars. Process in a boiling-water canner for 10 minutes (15 minutes at 1,000 to 6,000 feet; 20 minutes above 6,000 feet).
Jan Roberts-Dominguez

Please post the results after you try it.

Thanks everyone. Dave - that is kinda what I was thinking. I do it with peppers. But I also peel off the char on the peppers. I didn't think of the mushy / chewy corn part though. I have never made a corn relish before - so I doubt I would notice if the texture was off - unless it was just horrible mushy glop. The corn was only on the grill for about 5 minutes - the ear I had for dinner last night still had plenty of crunch. I'm gonna give it a try. And after this - a pepper relish.
Thanks again for all your insight :) I'll let you know how it all turns out!