This casserole is one of those meals I reach for when I want pizza flavors without the fuss of dough, or when I need something hearty that still feels light. It’s a one-dish bake that calls for pantry-friendly ingredients and comes together with everyday techniques. The quinoa gives it a pleasant bite and protein, while the tomato sauce, veggies, and vegan mozzarella create that familiar pizza comfort.
I like making a big pan because it reheats well and suits weeknight dinners, potlucks, or a relaxed weekend lunch. The steps are straightforward: cook the quinoa, sauté the vegetables, combine everything, and bake until set. No need for special equipment or long ingredient lists.
Below you’ll find the exact ingredients and step-by-step directions I use, followed by practical notes on swaps, tools, storage, and troubleshooting. If you follow the order and small tips here, you’ll get a reliably satisfying, plant-based casserole every time.
What Goes In
Ingredients
- 1 cup white quinoa (uncooked) — the main grain base; rinsing removes bitterness from the outer coating.
- 1 yellow onion — provides sweetness and structure when sautéed.
- 1 green bell pepper — adds a fresh, slightly sweet bite and color.
- 8 oz. mushrooms — give meaty texture and umami depth; slice or dice to your liking.
- 4 cloves garlic — fragrant backbone; mince finely so it distributes through the casserole.
- 1 cup fresh baby spinach — wilts down to add color, nutrition, and moisture.
- 3 roma tomatoes — diced, they add bright acidity and texture contrast to the sauce.
- 15 oz. can tomato sauce — the saucy, pizza-like binder for the quinoa and veggies.
- 3/4 cup vegan mozzarella shreds — adds creaminess and melty familiarity; reserve a little for the top if you like visible cheese.
- 2 tsp Italian seasoning — the herb blend that gives the casserole its pizza profile.
- 2 Tbsp. fresh basil (for serving) — chopped and added at the end for freshness and aroma.
Pizza Quinoa Casserole (Vegan!): Step-by-Step Guide
- Preheat oven to 375°F (190°C).
- Rinse 1 cup white quinoa under cold water. In a saucepan combine the rinsed quinoa and 1.5 cups water; bring to a light boil, then cover, reduce heat to low, and simmer 15–20 minutes or until the liquid is absorbed. Remove from heat, keep covered 5 minutes, then fluff with a fork.
- While the quinoa cooks, prepare the vegetables: dice 1 yellow onion, 1 green bell pepper, and 8 oz. mushrooms; mince 4 cloves garlic; chop 1 cup fresh baby spinach; dice 3 roma tomatoes; chop 2 Tbsp fresh basil and set aside for serving.
- Heat a large skillet over medium-high. Add the diced onion, bell pepper, and mushrooms. If you prefer a no‑oil sauté, add about 3 Tbsp water or broth to the skillet to prevent sticking. Sauté 7–8 minutes, stirring occasionally, until the vegetables are softened.
- Add the minced garlic, chopped spinach, and 2 tsp Italian seasoning to the skillet. Stir and sauté 1–2 minutes, until the garlic is fragrant and the spinach has wilted. Turn off the heat.
- In a large mixing bowl combine the cooked quinoa, the sautéed vegetables, the 15 oz. can tomato sauce, the diced roma tomatoes, and 3/4 cup vegan mozzarella shreds. (If you want some cheese visible on top, reserve a small portion of the 3/4 cup before stirring and set it aside for sprinkling.)
- Spread the mixture evenly into a 9×13-inch baking dish and gently press down. If you reserved any cheese, sprinkle it over the top now.
- Bake for 25 minutes. Remove from the oven and let the casserole rest 5–10 minutes to set.
- Garnish with the chopped 2 Tbsp fresh basil before serving.
Why It’s Crowd-Pleasing
This casserole hits familiar pizza notes — tomato, herbs, melty vegan cheese — while offering a satisfying, slightly nutty base in quinoa. It’s visually appealing: the red sauce, specks of basil, and melted cheese make it look like a comfort classic. Texture-wise, you get a mix of tender vegetables, toothsome quinoa, and gooey vegan cheese. That variety keeps forks coming back.
It also scales well. A 9×13 pan feeds a family, but you can halve the recipe for two people without losing the experience. Because the flavors are straightforward and well-loved (tomato, garlic, Italian seasoning), picky eaters often find it approachable. And it travels and reheats cleanly — great for potlucks or meal prep.
Vegan & Vegetarian Swaps
If you want to tailor the casserole, here are simple directions that don’t change the main recipe amounts:
- Vegan cheese options: use any plant-based shredded cheese you prefer instead of vegan mozzarella shreds. No extra measurements needed — stick with 3/4 cup for the balance the recipe expects.
- Grain substitution: if you’re not into quinoa, cooked brown rice or farro could work as a swap in practice, but I recommend keeping the original quinoa amount for texture parity.
- Add-ins: fold in sliced olives, artichoke hearts, or pre-cooked plant-based sausage if you want more pizza-style toppings; add these sparingly, as you’re not changing the main quantities.
Toolbox for This Recipe
- 9×13-inch baking dish — primary vessel for baking and serving.
- Medium saucepan with lid — for cooking quinoa.
- Large skillet — for sautéing the vegetables.
- Mixing bowl (large) — to combine quinoa, veggies, sauce, and cheese.
- Fork or whisk — for fluffing quinoa and mixing the casserole.
- Sharp knife and cutting board — for prepping onion, pepper, mushrooms, tomatoes, and basil.
Troubles You Can Avoid
Quinoa issues
If quinoa turns out gummy, it was likely cooked with too much water or not fluffed after cooking. Follow the 1 cup quinoa to 1.5 cups water ratio, simmer covered, then remove from heat and let it steam for 5 minutes before fluffing with a fork.
Watery casserole
To prevent a soggy bake, be sure to sauté vegetables until they’re softened and some moisture has evaporated (7–8 minutes as written). Dice tomatoes to a medium size so they integrate rather than release excessive liquid. Let the casserole rest 5–10 minutes after baking; this helps it set and makes slicing cleaner.
Sticking in the skillet
If you sauté without oil, add small splashes of water or broth as needed to keep vegetables from sticking. Keep the heat moderate and scrape often until you have softened vegetables and evaporated most of the released liquid.
Nutrition-Minded Tweaks
Small swaps can nudge this casserole toward your nutrition goals without changing the recipe amounts. Use a low-sodium tomato sauce to reduce salt. Increase the spinach slightly if you want more greens — you can stir in an extra handful before baking (no specific measurement required). Choose a lower-fat vegan cheese if you’re watching calories, or cut the 3/4 cup in half and boost herbs and veggies for more volume.
Quinoa already contributes complete protein and fiber; adding beans (drained and rinsed) would raise protein and fiber further, but remember that will alter texture and volume, so add sparingly if you want to keep the bake set the same way.
Chef’s Notes
One chef’s habit I recommend: reserve a little vegan cheese before you stir the mixture if you want that melted-top look. It makes a nice presentation difference. Also, finely chopping the mushrooms and peppers yields a more integrated texture; larger chunks are great if you prefer distinct bites.
Don’t skip the 5–10 minute rest after baking. The casserole firms up and slices much more cleanly, which makes serving nicer and reduces spillage. If you’re short on time, a brief 5-minute rest still helps.
Best Ways to Store
Cool the casserole to near room temperature (no longer than two hours at room temp) before refrigerating. Transfer covered to the refrigerator and consume within 3–4 days for best quality. Reheat individual portions in the microwave or reheat the entire pan in a 350°F (175°C) oven until warmed through.
For longer storage, freeze portions in airtight containers or wrapped foil for up to 2 months. Thaw overnight in the refrigerator before reheating. Expect a slight texture change after freezing, but the flavor holds up well.
Common Qs About Pizza Quinoa Casserole (Vegan!)
Can I make this gluten-free? Yes. The recipe as written is gluten-free if your tomato sauce and vegan cheese are certified gluten-free.
Is there a stovetop version? You could gently heat the combined mixture in a skillet and let it steam until warmed and set, but baking gives a firmer set and the slight browning on top that mimics baked pizzas.
Can I use pre-cooked quinoa? Yes. If you start with cooked quinoa, fold it into the mixture without cooking; you’ll skip step 2 and simply combine and bake. Keep volume in mind: 1 cup uncooked quinoa yields roughly 3 cups cooked quinoa.
How can I make it spicier? Stir in a pinch of red pepper flakes or a splash of hot sauce to the tomato sauce portion before combining. Add to taste.
Can I prepare parts ahead? Absolutely. Cook the quinoa and sauté the vegetables a day ahead, store them separately in the fridge, and assemble and bake when ready. Assembling ahead is fine too, but let the casserole sit at room temperature only briefly before baking.
Ready to Cook?
If you’ve got your quinoa rinsed and the vegetables prepped, this casserole moves quickly. Follow the steps in order, give the casserole those final minutes to set after baking, and don’t skimp on fresh basil at the end — it brightens every forkful.
It’s a reliable, cozy dish that leans plant-forward without sacrificing the pleasure of pizza. Make it for a weeknight, bring it to a gathering, or portion it for lunches. If you try it, tweak one small thing — a different vegan cheese or an extra handful of spinach — and you’ll have your personalized version in no time. Happy cooking.
Pizza Quinoa Casserole (Vegan!)
Ingredients
Ingredients
- 1 cupwhite quinoa uncooked
- 1 yellow onion
- 1 green bell pepper
- 8 oz.mushrooms
- 4 clovesgarlic
- 1 cupfresh baby spinach
- 3 roma tomatoes
- 15 oz.can tomato sauce
- 3/4 cupvegan mozzarella shreds*
- 2 tsp.Italian seasoning
- 2 Tbsp.fresh basil for serving
Instructions
Instructions
- Preheat oven to 375°F (190°C).
- Rinse 1 cup white quinoa under cold water. In a saucepan combine the rinsed quinoa and 1.5 cups water; bring to a light boil, then cover, reduce heat to low, and simmer 15–20 minutes or until the liquid is absorbed. Remove from heat, keep covered 5 minutes, then fluff with a fork.
- While the quinoa cooks, prepare the vegetables: dice 1 yellow onion, 1 green bell pepper, and 8 oz. mushrooms; mince 4 cloves garlic; chop 1 cup fresh baby spinach; dice 3 roma tomatoes; chop 2 Tbsp fresh basil and set aside for serving.
- Heat a large skillet over medium-high. Add the diced onion, bell pepper, and mushrooms. If you prefer a no‑oil sauté, add about 3 Tbsp water or broth to the skillet to prevent sticking. Sauté 7–8 minutes, stirring occasionally, until the vegetables are softened.
- Add the minced garlic, chopped spinach, and 2 tsp Italian seasoning to the skillet. Stir and sauté 1–2 minutes, until the garlic is fragrant and the spinach has wilted. Turn off the heat.
- In a large mixing bowl combine the cooked quinoa, the sautéed vegetables, the 15 oz. can tomato sauce, the diced roma tomatoes, and 3/4 cup vegan mozzarella shreds. (If you want some cheese visible on top, reserve a small portion of the 3/4 cup before stirring and set it aside for sprinkling.)
- Spread the mixture evenly into a 9x13-inch baking dish and gently press down. If you reserved any cheese, sprinkle it over the top now.
- Bake for 25 minutes. Remove from the oven and let the casserole rest 5–10 minutes to set.
- Garnish with the chopped 2 Tbsp fresh basil before serving.
Equipment
- Oven
- Saucepan
- Large Skillet
- Large Mixing Bowl
- 9x13 inch Baking Dish
- Fork
Notes
*Oil-free option:
Omit vegan cheese shreds. Substitute with up to 1/4 cup nutritional yeast for cheesy flavor if desired. You'll also want to add salt to taste to enhance the flavors.
Originally published March 2013. Updated April 2023.
