In a large stockpot, combine vinegar, sugar, water, canning salt, oregano and fennel seed. Bring to a boil.
Add cauliflower, carrots, celery and onions; return to a boil.
Remove from heat; add peppers.
Carefully ladle hot mixture into 10 hot 1-pint jars, leaving ½- in. headspace.
Add a bay leaf and 2 peppercorns to each jar; divide garlic slices among jars.
Remove air bubbles and adjust headspace, if necessary, by adding more hot mixture.
Wipe rims. Center lids on jars; screw on bands until fingertip tight.
Place jars into canner with simmering water, ensuring that they are completely covered with water.
Bring to a boil; process for 10 minutes.
Remove jars and cool.
