Heat olive oil in a Dutch oven or large deep skillet over medium heat.

Add onions and cook, stirring occasionally, until softened, about 4-6 minutes.

Add butternut squash, red bell pepper, garlic, oregano, and red pepper flakes; cook, stirring, for 2 minutes.

Pour in vegetable broth and increase heat to high, bringing to a boil.

Reduce heat to low, cover, and simmer for 10 minutes.

Stir in diced tomatoes and chickpeas, return to a simmer.

Cover and continue to simmer until the squash is tender but not mushy, approximately 8-10 minutes.

Prepare the gremolata: In a small bowl, combine chopped parsley, grated lemon peel, and minced garlic.

Toss gremolata ingredients together with a fork until well blended.

Season the stew with salt and freshly ground pepper to taste.

Serve the stew hot, sprinkled generously with gremolata.