Start by dicing all the yellow squash, eggplant, and zucchinis into ½-1 inch cubes. Place squashes into large bowl and set aside.
Next, dice the bell peppers and tomatoes into ½ inch pieces. Dice the onion and cut up the fresh basil. I like to keep these ingredients on my cutting board, but feel free to move around to separate plate or bowl if needed.
Once everything is diced and chopped, take out a medium-large pot. I like to use my 7 qt dutch oven for this recipe because it allows for this dish to simmer on a lower heat.
Put ¼ cup of olive oil in the pot on medium-high heat.
Once oil is heated, add your large bowl ingredients. Thoroughly stir the squashes to coat evenly in the olive oil. Add the salt and pepper and cook the squashes for about 8-10 minutes or until just brown. The squashes should be slightly soft, but not fully cooked yet. Remove the cooked squashes from the heat and place back into the large bowl.
Next, move the pot back to the stove and reduce heat to medium low. Add the remaining desired amount of olive oil (at least 2 tbsp) and place your minced garlic and yellow onion. Cook until bubbly and fragrant, about 1 minute.
Add the bell peppers and roma tomatoes to the onion/garlic and cook until peppers are soft and tomatoes are broken down. About 5 minutes.
Now take the previously cooked squashes and fresh basil and add them to the pot. Stir well.
Add the dried herbs and any additional salt and pepper to taste.
Pour the canned tomatoes into the mixture and stir to combine.
To finish this dish you will need to allow for it to come to a simmer. Cover the pot and keep on low heat to simmer, stirring occasionally. You will begin to smell the vegetables melding into one another after about 20-30 minutes.
For deeper flavor, place your cooled pot in the fridge overnight.* However, after simmering for 20-30 minutes your dish is ready to enjoy. Pair this easy ratatouille with buttered bread, pasta, rice, or just on its own!