Line 2 baking sheets with parchment paper and preheat oven to 400° on convection roast or 425° regular roast.
Rinse and drain peppers. Slice around the top of each pepper and pop off, removing most of seeds and veins. Arrange peppers on baking sheets without overcrowding.
For oven method, roast in upper portion of the oven for about 10 minutes, or until skins are darkening. Turn over and continue to roast for 10 more minutes or until other side is darkening.
For BBQ method, set outdoor grill to high heat on all burners. Arrange peppers on grill and allow to get well charred, turning often. Remove from grill when peppers have lots of dark skin all over and are softening.
Place roasted peppers in a bowl or pot and cover with lid. Leave covered until peppers are cool enough to handle, about 15 minutes.
While peppers are cooling, fill canner pot with enough water to completely cover jars. Set over burner on high and bring to a boil.
Peel garlic cloves and cut in half. Place one half in each jar.
Peel and/or scrape skin off peppers. Cut into slices or strips. Add pepper strips to jars, packing in well. Do not over fill, leave about 1/2 inch of space at the top of each jar.
Sprinkle 1 tsp of vinegar over each jar, then top with some olive oil. Using a skewer or similar tool, poke into jars to release any air bubbles and allow oil to distribute evenly. Top with more oil if necessary to completely cover peppers. Remember not to overfill.
Wipe rim of each jar with damp cloth. Top with new seals and rings.
When canning pot has reached a full boil, arrange jars on rack without crowding and lower into pot. Cover and boil for about 7 minutes. Depending on the number of jars you are making, you may have to process the jars in batches.
If you don't have a canner pot with a rack, place a kitchen towel in the bottom of a large pot and carefully lower jars into the pot using heat safe rubber oven mitts.
Cool jars on a towel on the counter.