Preheat Oven: Preheat the oven to 375 F and grease (or use cooking spray) a 8x8 inch square baking dish or line with parchment paper. Set the baking dish aside.
Roast Potatoes: Line a baking sheet with parchment paper and add the potatoes, thyme, oregano and 2 tsp of the oil. Season with a pinch of salt and pepper. Roast potatoes for 20-22 min, flipping halfway through, until tender and golden-brown. Note: To reduce cooking time, you can use pre-roasted/cooked potatoes or hash browns here or have a make-ahead option of roasting potatoes the day before.
Blend Batter: To a blender, add tofu, chickpea flour, water, nutritional yeast, garlic powder, turmeric, salt and pepper. Blend on high until smooth. Set aside.
Cook Vegetables: In a large non-stick pan, heat the remaining 2 tsp oil over medium heat. When the oil is hot, add onions, peppers and mushrooms. Season with a pinch of salt and pepper. Cook for 4-6 min, stirring occasionally, until softened.
Mix Batter: To a large bowl, add veggie mixture, roasted potatoes and batter and stir to combine.
Bake: Transfer the batter to the baking dish and bake on the middle rack of the oven for 45-50 minutes, until the top is golden brown and firm to the touch.
Serve: Let sit for 15 minutes, then slice and serve as desired.