This is my grandmother's recipe...
Clean either 24 pint-size or 12 quart-size canning jars. Chop enough green tomatoes to fill half the jars. Chop enough green peppers to fill a quarter of the jars. Chop enough onion to fill a quarter of the jars. Thoroughly mix the veggies and distribute evenly into jars.
In a large pot, dissolve 1 package of Mrs Wages Pickling Spices for Vegetables (crush the peppercorns) and 12 cups of granulated sugar into 8 cups of vinegar and 4 cups of water. Optionally add a Tbsp or two of celery seed. Distribute liquid mixture evenly over veggies in jars.
Process in pressure cooker at 15 psi for 15 minutes.