Heat a grill or grill pan over medium. Working in batches, if necessary, cook the sausages, turning occasionally, until an instant-read thermometer inserted into the centers registers 160°, 18 to 22 minutes.
Brush the vegetables with the olive oil and season with the oregano and salt and pepper. Grill the vegetables, turning occasionally, until tender, 10 to 12 minutes for the peppers and 12 to 15 minutes for the onions. Prep them as follows: Set aside 8 whole sausages; slice 5 sausages lengthwise; slice enough sausages to measure 4 cups; and chop enough sausages to measure 2 cups. Chop enough peppers to measure 3 cups and slice enough to measure 2 cups. Slice enough onions to measure 1 1/4 cups and chop enough to measure 1 1/2 cups plus 1/3 cup. Cool completely before storing.
Portion the sausages, onions and peppers into freezer bags labeled by recipe. Pasta: 2 cups sliced sausages, 1 cup sliced peppers and 1/2 cup sliced onions. Soup: 2 cups sliced sausages, 3/4 cup chopped peppers and 1/2 cup chopped onions. Squash: 3/4 cup chopped peppers and 1/3 cup chopped onions. Paella: 2 cups chopped sausages, 1 cup chopped peppers and 1/2 cup chopped onions. Sausages & Mash: 8 whole sausages and 1/2 cup each chopped peppers and onions. Sandwiches: 5 sausages sliced lengthwise, 1 cup sliced peppers and 3/4 cup sliced onions. Press out air, seal and freeze up to 2 months. Thaw in the fridge overnight or microwave on the defrost setting about 7 minutes.