Heat olive oil in a large nonstick skillet over medium-high heat.
Add onions, poblanos, and jalapenos. Cook for 5 minutes, stirring occasionally, until vegetables begin to soften.
Add corn and tomatoes. Cook for 5 more minutes, stirring occasionally.
Add zucchini, yellow squash, garlic, salt, black pepper, oregano and ground cumin. Stir to combine and cook for 5 minutes, stirring every minute or so.
Add water to skillet, reduce heat to low, cover and simmer for 5 minutes.
Uncover the skillet, add the shredded cheese and milk, and stir together until the cheese has fully melted.
Remove from heat, garnish with chopped cilantro and cotija cheese, and serve.