Slice all veggies.

Add sliced bell pepper and onion to a skillet with enough water to cover the bottom of the pan. Sauté.

While the pepper and onion sauté, add sliced squash and zucchini to a griddle and let cook,.

Toast bread.

Prepare guacamole.

Once everything has cooked, spread a thin layer of guacamole on one side of each slice of bread. (This will help keep everything together.)

Layer zucchini, squash, and the sautéed peppers and onions and the bread.