Heat olive oil in a large Dutch oven or heavy-bottomed pot over medium heat. Add diced onion and cook for 4-5 minutes until softened and translucent, stirring occasionally to prevent browning and develop sweetness.

Add minced garlic and cook for 1 minute until fragrant. The stunning summer meatless character begins here with these aromatic foundations, so don't rush past this step—precision matters.

Add chopped zucchini, yellow squash, and both bell peppers to the pot. Stir continuously for 3-4 minutes to lightly soften the vegetables and release their natural moisture without overcooking them.

Add halved cherry tomatoes and the can of diced tomatoes (with juice). Stir gently and let this combination simmer for 2 minutes to begin breaking down the tomatoes and creating a light sauce base.

Pour in vegetable broth slowly while stirring. Add dried oregano, salt, and black pepper, then bring the entire mixture to a gentle boil over medium-high heat. This is when the beautiful summer vegetable stew recipe comes together structurally—the vegetables will begin softening uniformly.

Reduce heat to medium-low and let simmer uncovered for 12-15 minutes until the zucchini and squash are fork-tender but not mushy. Taste the broth; it should taste balanced and flavorful, never thin or underseasoned.

Drain and add cannellini beans, stirring gently. Simmer for 2 more minutes to warm them through. Remove from heat and stir in fresh basil and balsamic vinegar—the acid provides complexity that transforms this into an elegant dish worthy of dinner guests.